Hybrid common/independent FD-basis for type II CSI enhancement

ABSTRACT

A method performed by a wireless device (510, 700, 1000) for transmitting a channel state information (CSI) report for a downlink channel comprises obtaining (601) a first set of candidate frequency-domain components and determining (602) a set of spatial-domain components. The method comprises determining (603) a second set of candidate frequency-domain components as a subset of the first set of candidate frequency-domain components. The method comprises determining (604), for each spatial-domain component of the set of spatial-domain components, a spatial-domain component-specific set of frequency-domain components as a subset of the second set of candidate frequency-domain components. The method comprises transmitting (605), to a network node (560, 900), the CSI report.

PRIORITY

The present application is a continuation under 35 U.S.C. 111(a) ofco-pending International Patent Application Serial No. PCT/SE2019/051065filed Oct. 28, 2019 and entitled “Hybrid Common/Independent FD-Basis forType II CSI Enhancement” which claims priority to U.S. ProvisionalPatent Application No. 62/755,174 filed Nov. 2, 2018 both of which arehereby incorporated by reference in their entirety.

TECHNICAL FIELD

The present disclosure relates, in general, to wireless communicationsand, more particularly, to hybrid common/independent frequencyduplex-basis for Type II channel state information enhancement.

BACKGROUND

Multi-antenna techniques can significantly increase the data rates andreliability of a wireless communication system. Equipping both thetransmitter and the receiver with multiple antennas results in amultiple-input multiple-output (MIMO) communication channel thatimproves performance. Such systems and/or related techniques arecommonly referred to as MIMO.

The New Radio (NR) standard is currently evolving with enhanced MIMOsupport. A core component in NR is the support of MIMO antennadeployments and MIMO-related techniques, such as spatial multiplexing.The spatial-multiplexing mode aims for high data rates in favorablechannel conditions.

FIG. 1 illustrates a transmission structure 100 of precoded spatialmultiplexing mode in NR. In the spatial multiplexing operation depictedin FIG. 1, the information carrying symbol vector s is multiplied by anN_(T)×r precoder matrix W, which serves to distribute the transmitenergy in a subspace of the N_(T) (corresponding to N_(T) antenna ports)dimensional vector space. The precoder matrix is typically selected froma codebook of possible precoder matrices. The precoder matrix istypically indicated by means of a precoder matrix indicator (PMI), whichspecifies a unique precoder matrix in the codebook for a given number ofsymbol streams. The transmission rank (r) symbols in symbol vector seach correspond to a layer In this way, spatial multiplexing is achievedsince multiple symbols can be transmitted simultaneously over the sametime/frequency resource element (TFRE). The number of symbols r istypically adapted to suit the current channel properties.

NR uses orthogonal frequency division multiplexing (OFDM) in thedownlink (DL) and discrete Fourier transform (DFT) precoded OFDM in theuplink (UL). Hence, the received N_(R)×1 vector y_(n) for a certain TFREon subcarrier n (or alternatively data TFRE number n) is thus modeledby:y _(n) =H _(n) Ws _(n) +e _(n)where e_(n) is a noise/interference vector obtained as realizations of arandom process. The precoder W can be a wideband precoder, which isconstant over frequency, or precoder W can be frequency selective.

The precoder matrix W is often chosen to match the characteristics ofthe N_(R)×N_(T) MIMO channel matrix H_(n), resulting in so-calledchannel dependent precoding. This is also referred to as closed-loopprecoding and essentially strives to focus the transmit energy into asubspace that is strong in the sense of conveying much of thetransmitted energy to the user equipment (UE).

In closed-loop precoding for the NR DL, the UE transmits recommendationsto the base station (e.g., a gNodeB (gNB) in NR) of a suitable precoderto use. The UE bases these recommendations on channel measurements inthe forward link (DL). In the case of NR, the gNB configures the UE toprovide feedback according to CSI-ReportConfig. The gNB may transmitchannel state information reference signals (CSI-RS) and may configurethe UE to use measurements of CSI-RS to feed back recommended precodingmatrices that the UE selects from a codebook. A single precoder that issupposed to cover a large bandwidth (wideband precoding) may be fedback. It may also be beneficial to match the frequency variations of thechannel and instead feed back a frequency-selective precoding report(e.g., several precoders, one per sub-band). This is an example of themore general case of channel state information (CST) feedback, whichalso encompasses feeding back other information than recommendedprecoders to assist the gNB in subsequent transmissions to the UE. Suchother information may include channel quality indicators (CQIs) as wellas transmission rank indicator (RI). In NR, CSI feedback can be eitherwideband, where one CSI is reported for the entire channel bandwidth, orfrequency-selective, where one CSI is reported for each sub-band, whichis defined as a number of contiguous resource blocks (RBs). Currently inNR, a sub-band ranges between 4 and 32 physical resource blocks (PRBs),depending on the bandwidth part (BWP) size, but more generally asub-band can comprise any amount of PRBs.

Given the CSI feedback from the UE, the gNB determines the transmissionparameters it wishes to use to transmit to the UE, including theprecoding matrix, transmission rank, and modulation and coding scheme(MCS). These transmission parameters may differ from the recommendationsthat the UE makes. The number of columns of the precoder W reflects thetransmission rank, and thus the number of spatially multiplexed layers.For efficient performance, it is important to select a transmission rankthat matches the channel properties.

Two-Dimensional Antenna Arrays

Two-dimensional antenna arrays may be (partly) described by the numberof antenna columns corresponding to the horizontal dimension N_(h), thenumber of antenna rows corresponding to the vertical dimension N_(v),and the number of dimensions corresponding to different polarizationsN_(p). The total number of antennas is thus N=N_(h)N_(v)N_(p). Note thatthe concept of an antenna is non-limiting in the sense that it can referto any virtualization (e.g., linear mapping) of the physical antennaelements. For example, pairs of physical sub-elements could be fed thesame signal, and hence share the same virtualized antenna port.

FIG. 2 illustrates a two-dimensional antenna array of cross-polarizedantenna elements. More particularly, FIG. 2 illustrates an example of a4×4 antenna array 200 with cross-polarized antenna elements. In theexample of FIG. 2, the two-dimensional antenna array of cross-polarizedantenna elements (N_(p)=2) has N_(h)=4 horizontal antenna elements andN_(v)=4 vertical antenna elements.

Precoding may be interpreted as multiplying the signal with differentbeamforming weights for each antenna prior to transmission. One approachis to tailor the precoder to the antenna form factor (i.e., taking intoaccount N_(h), N_(v) and N_(p) when designing the precoder codebook).

Channel State Information Reference Signals (CSI-RS)

For CSI measurement and feedback, CSI-RS are defined. A CSI-RS istransmitted on each transmit antenna (or antenna port) and is used by aUE to measure the DL channel between each of the transmit antenna portsand each of its receive antenna ports. The antenna ports are alsoreferred to as CSI-RS ports. The number of antenna ports currentlysupported in NR are {1,2,4,8,12,16,24,32}. By measuring the receivedCSI-RS, a UE can estimate the channel that the CSI-RS is traversing,including the radio propagation channel and antenna gains. The CSI-RSfor the above purpose is also referred to as Non-Zero Power (NZP)CSI-RS.

CSI-RS can be configured to be transmitted in certain slots and incertain resource elements (REs) in a slot.

FIG. 3 illustrates an example of RE allocation for a 12-port CSI-RS inNR 300. In the example of CSI-RS REs for 12 antenna ports illustrated inFIG. 3, one RE per RB per port is shown.

In addition, an interference measurement resource (IMR) is also definedin NR for a UE to measure interference. An IMR contains 4 REs, either 4adjacent RE in frequency in the same OFDM symbol or 2 by 2 adjacent REsin both time and frequency in a slot. By measuring both the channelbased on NZP CSI-RS and the interference based on an IMR, a UE canestimate the effective channel and noise plus interference to determinethe CSI (i.e., rank, precoding matrix, and the channel quality).

Furthermore, a UE in NR may be configured to measure interference basedon one or multiple NZP CSI-RS resources.

CSI Framework in NR

In NR, a UE can be configured with multiple CSI reporting settings andmultiple CSI-RS resource settings. Each resource setting can containmultiple resource sets, and each resource set can contain up to 8 CSI-RSresources. For each CSI reporting setting, a UE feeds back a CSI report.Each CSI reporting setting may contain some or all of the followinginformation: a CSI-RS resource set for channel measurement; an IMRresource set for interference measurement; a CSI-RS resource set forinterference measurement; time-domain behavior (i.e., periodic,semi-persistent, or aperiodic reporting); frequency granularity (i.e.,wideband or sub-band); CSI parameters to be reported such as RI, PMI,CQI, and CSI-RS resource indicator (CRI) in case of multiple CSI-RSresources in a resource set; codebook types (i.e., Type I or Type II);codebook subset restriction; measurement restriction; and sub-band size.With respect to sub-band size, one out of two possible sub-band sizes isindicated. The value range depends on the bandwidth of the BWP. OneCQI/PMI (if configured for sub-band reporting) is fed back per sub-band.

When the CSI-RS resource set in a CSI reporting setting containsmultiple CSI-RS resources, one of the CSI-RS resources is selected by aUE and a CSI-RS Resource Indicator (CRI) is also reported by the UE toindicate to the gNB about the selected CSI-RS resource in the resourceset, together with RI, PMI and CQI associated with the selected CSI-RSresource.

For aperiodic CSI reporting in NR, more than one CSI reporting setting,each with a different CSI-RS resource set for channel measurement and/orresource set for interference measurement can be configured andtriggered at the same time. In this case, multiple CSI reports areaggregated and sent from the UE to the gNB in a single Physical UplinkShared Channel (PUSCH).

DFT-Based Precoders

One type of precoding uses a DFT-precoder, where the precoder vectorused to precode a single-layer transmission using a single-polarizeduniform linear array (ULA) with N antennas is defined as:

${{w_{1\; D}(k)} = {\frac{1}{\sqrt{N}}\begin{bmatrix}e^{j\; 2\;{\pi\; \cdot 0 \cdot \frac{k}{QN}}} \\e^{j\; 2\;{\pi \cdot 1 \cdot \frac{k}{QN}}} \\\vdots \\e^{j\; 2\;{\pi \cdot {({N - 1})} \cdot \frac{k}{QN}}}\end{bmatrix}}},$where k=0, 1, . . . QN−1 is the precoder index and Q is an integeroversampling factor. A corresponding precoder vector for atwo-dimensional uniform planar array (UPA) can be created by taking theKronecker product of two precoder vectors as:w _(2D)(k,l)=w _(1D)(k)⊗w _(1D)(l).Extending the recoder for a dual-polarized UPA may then be done as:

${w_{{2D},{DP}}\left( {k,l,\phi} \right)} = {{\begin{bmatrix}1 \\e^{j\;\phi}\end{bmatrix} \otimes {w_{2D}\left( {k,l} \right)}} = {\quad{{\begin{bmatrix}{w_{2D}\left( {k,l} \right)} \\{e^{j\;\phi}{w_{2\; D}\left( {k,l} \right)}}\end{bmatrix} = {\begin{bmatrix}{w_{2D}\left( {k,l} \right)} & 0 \\0 & {w_{2\; D}\left( {k,l} \right)}\end{bmatrix}\begin{bmatrix}1 \\e^{j\;\phi}\end{bmatrix}}},}}}$where e^(jϕ) is a co-phasing factor that may, for instance, be selectedfrom Quadrature Phase Shift Keying (QPSK) alphabet

$\phi \in {\left\{ {0,\frac{\pi}{2},\pi,\frac{3\pi}{2}} \right\}.}$

A precoder matrix W_(2D,DP) for multi-layer transmission may be createdby appending columns of DFT precoder vectors as:W _(2D,DP)=[w _(2D,DP)(k ₁ ,l ₁,ϕ₁)w _(2D,DP)(k ₂ ,l ₂,ϕ₂) . . . w_(2D,DP)(k _(R) ,l _(R),ϕ_(R))],where R is the number of transmission layers (i.e., the transmissionrank). In a special case for a rank-2 DFT precoder, k₁=k₂=k and l₁=l₂=l,meaning that.

$W_{{2\; D},{DP}} = {\quad{\left\lbrack {{w_{{2D},{DP}}\left( {k,l,\phi_{1}} \right\rbrack}{w_{{2D},{DP}}\left( {k,l,\phi_{2}} \right)}} \right\rbrack = {{\begin{bmatrix}{w_{2D}\left( {k,l} \right)} & 0 \\0 & {w_{2\; D}\left( {k,l} \right)}\end{bmatrix}\begin{bmatrix}1 & 1 \\e^{j\;\phi_{1}} & e^{j\;\phi_{2}}\end{bmatrix}}.}}}$Such DFT-based precoders are used, for example, in NR Type I CSIfeedback.

Multi-User MIMO (MU-MIMO)

With MU-MIMO, two or more users in the same cell are co-scheduled on thesame time-frequency resource. That is, two or more independent datastreams are transmitted to different UEs at the same time, and thespatial domain is used to separate the respective streams. Bytransmitting several streams simultaneously, the capacity of the systemcan be increased. This, however, comes at the cost of reducing thesignal-to-interference-plus-noise ratio (SINR) per stream, as the powermust be shared between streams and the streams will cause interferenceto each-other.

Multi-Beam (Linear Combinations) Precoders

One central part of MU-MIMO is obtaining accurate CSI that enablesnullforming between co-scheduled users. Therefore, support has beenadded in Long Term Evolution (LTE) Release 14 (Rel-14) and NR Release 15(Rel-15) for codebooks that provide more detailed CSI than thetraditional single DFT-beam precoders. These codebooks are referred toas Advanced CSI (in LTE) or Type II codebooks (in NR) and can bedescribed as a set of precoders where each precoder is created frommultiple DFT beams. A multi-beam precoder may be defined as a linearcombination of several DFT precoder vectors as:

${w = {\sum\limits_{i}{c_{i} \cdot {w_{{2D},{DP}}\left( {{k_{i}.l_{i}},\phi_{i}} \right)}}}},$where {c_(i)} may be general complex coefficients. Such a multi-beamprecoder may more accurately describe the UE's channel and may thusbring an additional performance benefit compared to a DFT precoder,especially for MU-MIMO where rich channel knowledge is desirable inorder to perform nullforming between co-scheduled UEs.

NR Rel-15

For the NR Type II codebook in Rel-15, the precoding vector for eachlayer and sub-band is expressed in 3^(rd) Generation Partnership Project(3GPP) TS 38.214 v15.3.0 as:

${W_{q_{1},q_{2},n_{1},n_{2},p_{i}^{(i)},p_{i}^{(2)},c_{i}}^{l} = {\frac{1}{\sqrt{N_{1}N_{2}{\sum\limits_{i = 0}^{{2L} - 1}\left( {p_{l,i}^{(1)}p_{l,i}^{(2)}} \right)^{2}}}}\begin{bmatrix}{\sum\limits_{i = 0}^{L - 1}{v_{m_{i}^{(i)},m_{2}^{(i)}}p_{l,i}^{(1)}p_{l,i}^{(2)}\varphi_{l,i}}} \\{\sum\limits_{i = 0}^{L - 1}{v_{m_{i}^{(i)},m_{2}^{(i)}}p_{l,{i + L}}^{(1)}p_{l,{i + L}}^{(2)}\varphi_{l,{i + L}}}}\end{bmatrix}}},{l = 1},2$

By restructuring the above formula and expressing it more simply, theprecoder vector w_(l,p)(k) can be formed for a certain layer l=0,1,polarization p=0,1 and resource block k=0, . . . , N_(RB)−1, as:

${w_{l,p}(k)} = {\frac{1}{C}{\sum\limits_{l = 0}^{L - 1}{v_{i}p_{l,i}^{(1)}{c_{l,i}(k)}\mspace{14mu}{where}}}}$${c_{l,i}(k)} = {{{p_{l,i}^{(2)}\left( \left\lfloor \frac{k}{s} \right\rfloor \right)}\mspace{11mu}{\varphi_{l,i}\left( \left\lfloor \frac{k}{s} \right\rfloor \right)}\mspace{14mu}{for}\mspace{14mu} p} = {0\mspace{14mu}{and}}}$${{c_{l,i}(k)} = {{{p_{i,{L + i}}^{(2)}\left( \left\lfloor \frac{k}{s} \right\rfloor \right)}\mspace{11mu}{\varphi_{i,{l + i}}\left( \left\lfloor \frac{k}{s} \right\rfloor \right)}\mspace{14mu}{for}\mspace{14mu} p} = 1}},$S is the sub-band size and N_(SB) is the number of sub-bands in the CSIreporting bandwidth. Hence, the change in a beam coefficient acrossfrequency c_(l,i)(k) is determined based on the 2N_(SB) parametersp_(l,i) ⁽²⁾(0), . . . , p_(l,i) ⁽²⁾(N_(SB)−1) and φ_(l,i)(0), . . . ,φ_(l,i)(N_(SB)−1), where the sub-band amplitude parameter p is quantizedusing 0-1 bit and the sub-band phase parameter φ_(l,i) is quantizedusing 2-3 bits, depending on codebook configuration.

Type II Overhead Reduction for NR Release 16 (Rel-16)

The Type II CSI feedback performance and overhead is sensitive to thesub-band size. The optimal Type II CSI beam coefficients can vary quiterapidly over frequency, and hence the more averaging that is performed(i.e., the larger the sub-band size), the more reduction in MU-MIMOperformance can be expected. Operation with Type II CSI is typicallycompared against reciprocity-based operation, where subcarrier-level CSIcan be obtained via SRS sounding. In the NR CSI reporting procedure,there are two possible CSI sub-band sizes defined for sub-band based CSIreporting for each number of PRBs of the BWP (i.e. the BWP bandwidth)and the gNB configures which of the two sub-band sizes to use as part ofthe CSI reporting configuration. For 10 MHz bandwidth using 15 kHzsubcarrier spacing (SCS), which is a typical LTE configuration, NRfeatures either seven 1.44 MHz sub-bands or thirteen 720 kHz sub-bands.However, for 100 MHz bandwidth using 30 kHz SCS, a typical NRconfiguration, NR features either nine 11.52 MHz sub-bands or eighteen5.76 MHz sub-bands. Such large sub-band sizes could result in poor CSIquality.

Overhead reductions are considered for NR Rel-16 Type 11. The rationaleis that it has been observed that there is a strong correlation betweendifferent values of c_(l,i)(k), for different values of k, and thiscorrelation could be exploited to perform efficient compression of theinformation in order to reduce the number of bits required to representthe information. This would lower the amount of information that needsto be signaled from the UE to the gNB, which is relevant from severalaspects. Both lossy (implying a potentially decreased level of qualityin the CSI) as well as lossless compression may be considered.

In the case of lossy compression, there are many ways to parametrize thebeam coefficients over frequency to achieve an appropriate CSI qualityvs. overhead trade-off. By keeping the basic structure of the precoderas described above, one may update the expression for c_(l,i)(k). Moregenerally, one can describe c_(l,i)(k) as a function ƒ(k, α₀, . . . ,α_(M−1)) that is based on the M parameters α₀, . . . , α_(M−1), wherethese M parameters in turn are represented using a number of bits thatcan be fed back as part of the CSI report.

As an example, consider the special case where ƒ(k, α₀, . . . , α_(M−1))constitutes a linear transformation. In this case, the function can beexpressed by using a transformation matrix:

${B = {\begin{bmatrix}b_{0,0} & \ldots & b_{0,K} \\\vdots & \ddots & \vdots \\b_{N_{RB},0} & \ldots & b_{N_{RB},K}\end{bmatrix} = \left\lbrack {b_{0}\mspace{11mu}\ldots\mspace{11mu} b_{K}} \right\rbrack}},$consisting of K number of N_(RB)×1 sized basis vectors along with acoefficient vector:

$a = \begin{bmatrix}\alpha_{0} \\\ldots \\\alpha_{K - 1}\end{bmatrix}$

Here, N_(RB) is the number of RBs in the CSI reporting bandwidth. Othergranularities and units of the basis vectors can also be considered,such as the number of sub-bands N_(SB), a subcarrier level granularitywith 12N_(RB)×1 size basis vectors, or a number of RBs.

For instance, the M parameters can be split up into a parameter I,selecting the K basis vectors from a set of basis vector candidates, andthe coefficients α₀, . . . , α_(K−1). That is, some index parameter Idetermines the basis matrix B, for instance, by selecting columns from awider matrix or by some other way. The beam coefficients may then beexpressed as:

${c_{l,i}(k)} = {{f\left( {k,I,a_{0},\ldots\mspace{14mu},a_{K - 1}} \right)} = {{\lbrack B\rbrack_{k,:}a} = {\sum\limits_{d = 0}^{K - 1}{b_{k,d}{a_{d}.}}}}}$That is, by forming a vector with all the beam coefficients (for a beam)such as.

${c_{l,i} = \begin{bmatrix}{c_{l,i}(0)} \\\ldots \\{c_{l,i}\left( {N_{RB} - 1} \right)}\end{bmatrix}},$that vector can be expressed as a linear transformation:c _(l,i) =Ba _(i).In fact, the entire precoder can be expressed using matrix formulation,which is good for illustrative purposes. The beam coefficients for allthe beams i and resource blocks k can be stacked into a matrix:

${C_{F} = \begin{bmatrix}c_{l,0}^{T} \\\ldots \\c_{l,{{2L} - 1}}^{T}\end{bmatrix}},$(where L is the number of beams) which then can be expressed as:

$C_{F} = {\begin{bmatrix}c_{l,0}^{T} \\\ldots \\c_{l,{{2L} - 1}}^{T}\end{bmatrix} = {\begin{bmatrix}{a_{0}^{T}B^{T}} \\\ldots \\{a_{{2L} - 1}^{T}B^{T}}\end{bmatrix} = {{\begin{bmatrix}a_{0}^{T} \\\ldots \\a_{{2L} - 1}^{T}\end{bmatrix}B^{T}} = {{\overset{\sim}{C}}_{F}{B^{T}.}}}}}$

The linear combination of beam basis vectors and beam coefficients canalso be expressed as a matrix product. This implies that the precoders(for all RBs) for a certain layer can be expressed as a matrix product:W _(F) =W ₁ C _(F) =W ₃ {tilde over (C)} _(F) B ^(T).That is, a spatial linear transformation (from antenna domain to beamdomain) is applied from the left by multiplication of W₁ and from theright a frequency linear transformation by multiplication of B^(T). Theprecoders are then expressed more sparsely using a smaller coefficientmatrix {tilde over (C)}_(F) in this transformed domain.

FIG. 4 illustrates a matrix representation 400 of the Type II overheadreduction scheme described above, where examples of the dimensions ofthe matrix components of the precoder are illustrated.

There currently exist certain challenges. For example, Type II precoderschemes may lead to better MU-MIMO performance, but at the cost ofincreased CSI feedback overhead and UE precoder search complexity. It isan open problem of how an efficient Type II codebook that results ingood MU-MIMO performance, but low feedback overhead, should beconstructed as well as how the CSI feedback should be derived by the UE.As another example, it is an open issue how to support higher rankrepresentations for Type II feedback. One problem is that the feedbackoverhead increases with the number of layers, which makes a high layerrepresentation infeasible.

SUMMARY

To address the foregoing problems with existing approaches, disclosed isa method performed by a wireless device for transmitting a CSI reportfor a downlink channel, the CSI report indicating a plurality ofprecoder vectors, wherein each of the precoder vectors corresponds to afrequency sub-band of the bandwidth of the downlink channel, a precodervector being expressed as a linear combination of spatial-domaincomponents and frequency-domain components, and wherein indicating theplurality of precoder vectors comprises indicating the frequency-domaincomponents and a set of linear combination coefficients. The methodcomprises obtaining a first set of candidate frequency-domaincomponents. The method comprises determining a set of spatial-domaincomponents. The method comprises determining a second set of candidatefrequency-domain components as a subset of the first set of candidatefrequency-domain components. The method comprises determining, for eachspatial-domain component of the set of spatial-domain components, aspatial-domain component-specific set of frequency-domain components asa subset of the second set of candidate frequency-domain components,wherein each frequency-domain component in the spatial-domaincomponent-specific set of frequency-domain components is associated witha non-zero coefficient of the set of linear combination coefficients.The method comprises transmitting, to a network node, the CSI reportcomprising an indication of: the determined second set of candidatefrequency-domain components; the determined spatial-domaincomponent-specific sets of frequency-domain components; and the non-zerocoefficients of the set of linear combination coefficients.

In certain embodiments, determining the second set of candidatefrequency-domain components as a subset of the first set of candidatefrequency-domain components may comprise: analyzing an estimate of thedownlink channel to determine one or more properties of the downlinkchannel; and selecting the second set of candidate frequency-domaincomponents from the first set of candidate frequency-domain componentsbased on the determined one or more properties of the downlink channel.

In certain embodiments, the candidate frequency-domain components may beorthogonal basis vectors In certain embodiments, the orthogonal basisvectors may be discrete Fourier transform vectors.

In certain embodiments, a size of the frequency sub-band may be aninteger number of PRBs.

In certain embodiments, determining the spatial-domaincomponent-specific set of frequency-domain components may comprisedetermining if the associated one or more linear combining coefficientsare non-zero.

In certain embodiments, obtaining the first set of candidatefrequency-domain components may comprise defining a first basisconstituting a number of basis vectors.

In certain embodiments, obtaining the first set of candidatefrequency-domain components may comprise one of: obtaining the first setof candidate frequency-domain components by accessing a predefinedtable; obtaining the first set of candidate frequency-domain componentsvia higher layer signaling; and determining the first set of candidatefrequency-domain components.

In certain embodiments, determining the second set of candidatefrequency-domain components as a subset of the first set of candidatefrequency-domain components may comprise creating a common basis for allspatial-domain components.

In certain embodiments, the first set of candidate frequency-domaincomponents may be a first basis matrix B comprising K basis vectors. Incertain embodiments, determining the second set of candidatefrequency-domain components as the subset of the first set of candidatefrequency-domain components may comprise selecting K_(c)<K columns ofthe first basis matrix B and concatenating the selected columns K_(c) toform a common basis matrix B_(c). In certain embodiments, the commonbasis matrix B_(c) may be chosen per one or more of polarization andlayer.

In certain embodiments, determining the spatial-domaincomponent-specific frequency-domain components may comprise selecting aselection of columns from the common basis matrix B_(c).

Also disclosed is a computer program, the computer program comprisinginstructions configured to perform the above-described method in awireless device.

Also disclosed is a computer program product, the computer programproduct comprising a non-transitory computer-readable storage medium,the non-transitory computer-readable storage medium comprising acomputer program comprising computer-executable instructions which, whenexecuted on a processor, are configured to perform the above-describedmethod in a wireless device.

Also disclosed is a wireless device configured to transmit a CSI reportfor a downlink channel, the CSI report indicating a plurality ofprecoder vectors, wherein each of the precoder vectors corresponds to afrequency sub-band of the bandwidth of the downlink channel, a precodervector being expressed as a linear combination of spatial-domaincomponents and frequency-domain components, and wherein indicating theplurality of precoder vectors comprises indicating the frequency-domaincomponents and a set of linear combination coefficients. The wirelessdevice comprises: a receiver; a transmitter; and processing circuitrycoupled to the receiver and the transmitter. The processing circuitry isconfigured to obtain a first set of candidate frequency-domaincomponents. The processing circuitry is configured to determine a set ofspatial-domain components. The processing circuitry is configured todetermine a second set of candidate frequency-domain components as asubset of the first set of candidate frequency-domain components. Theprocessing circuitry is configured to determine, for each spatial-domaincomponent of the set of spatial-domain components, a spatial-domaincomponent-specific set of frequency-domain components as a subset of thesecond set of candidate frequency-domain components, wherein eachfrequency-domain component in the spatial-domain component-specific setof frequency-domain components is associated with a non-zero coefficientof the set of linear combination coefficients. The processing circuitryis configured to transmit, to a network node, the CSI report comprisingan indication of: the determined second set of candidatefrequency-domain components; the determined spatial-domaincomponent-specific sets of frequency-domain components; and the non-zerocoefficients of the set of linear combination coefficients.

In certain embodiments, the processing circuitry configured to determinethe second set of candidate frequency-domain components as a subset ofthe first set of candidate frequency-domain components may be furtherconfigured to: analyze an estimate of the downlink channel to determineone or more properties of the downlink channel; and select the secondset of candidate frequency-domain components from the first set ofcandidate frequency-domain components based on the determined one ormore properties of the downlink channel.

In certain embodiments, the candidate frequency-domain components may beorthogonal basis vectors. In certain embodiments, the orthogonal basisvectors may be discrete Fourier transform vectors.

In certain embodiments, a size of the frequency sub-band may be aninteger number of PRBs.

In certain embodiments, the processing circuitry configured to determinethe spatial-domain component-specific set of frequency-domain componentsmay be further configured to: determine if the associated one or morelinear combining coefficients are non-zero.

In certain embodiments, the processing circuitry configured to obtainthe first set of candidate frequency-domain components may be furtherconfigured to define a first basis constituting a number of basisvectors.

In certain embodiments, the processing circuitry configured to obtainthe first set of candidate frequency-domain components may be furtherconfigured to: obtain the first set of candidate frequency-domaincomponents by accessing a predefined table; obtain the first set ofcandidate frequency-domain components via higher layer signaling; anddetermine the first set of candidate frequency-domain components.

In certain embodiments, the processing circuitry configured to determinethe second set of candidate frequency-domain components as a subset ofthe first set of candidate frequency-domain components may be furtherconfigured to create a common basis for all spatial-domain components.

In certain embodiments, the first set of candidate frequency-domaincomponents may be a first basis matrix B comprising K basis vectors. Incertain embodiments, the processing circuitry configured to determinethe second set of candidate frequency-domain components as the subset ofthe first set of candidate frequency-domain components may be furtherconfigured to select K_(c)<K columns of the first basis matrix B andconcatenate the selected columns K_(c) to form a common basis matrixB_(c). In certain embodiments, the common basis matrix B_(c) may bechosen per one or more of polarization and layer.

In certain embodiments, the processing circuitry configured to determinethe spatial-domain component-specific frequency-domain components may befurther configured to: select a selection of columns from the commonbasis matrix B_(c).

Also disclosed is a method performed by a network node for receiving aCSI report for a downlink channel, the CSI report indicating a pluralityof precoder vectors, wherein each of the precoder vectors corresponds toa frequency sub-band of the bandwidth of the downlink channel, aprecoder vector being expressed as a linear combination ofspatial-domain components and frequency-domain components, and whereinindicating the plurality of precoder vectors comprises indicating thefrequency-domain components and a set of linear combinationcoefficients. The method comprises receiving, from a wireless device,the CSI report comprising an indication of: a second set of candidatefrequency-domain components being a subset of a first set of candidatefrequency-domain components; one or more spatial-domaincomponent-specific sets of frequency-domain components being subsets ofthe second set of candidate frequency-domain components, eachfrequency-domain component in the one or more spatial-domaincomponent-specific sets of frequency-domain components being associatedwith non-zero coefficients of the set of linear combinationcoefficients; and the non-zero coefficients. The method comprisesdetermining one or more precoder vectors based upon the indicationreceived in the CSI report.

In certain embodiments, the method may further comprise using one of thedetermined one or more precoder vectors to perform a transmission to thewireless device.

In certain embodiments, the method may further comprise using adifferent precoder vector from the one or more determined precodervectors to perform a transmission to the wireless device.

In certain embodiments, a size of the frequency sub-band may be aninteger number of PRBs.

Also disclosed is a computer program, the computer program comprisinginstructions configured to perform the above-described method in anetwork node.

Also disclosed is a computer program product, the computer programproduct comprising a non-transitory computer-readable storage medium,the non-transitory computer-readable storage medium comprising acomputer program comprising computer-executable instructions which, whenexecuted on a processor, are configured to perform the above-describedmethod in a network node.

Also disclosed is a network node configured to receive a CSI report fora downlink channel, the CSI report indicating a plurality of precodervectors, wherein each of the precoder vectors corresponds to a frequencysub-band of the bandwidth of the downlink channel, a precoder vectorbeing expressed as a linear combination of spatial-domain components andfrequency-domain components, and wherein indicating the plurality ofprecoder vectors comprises indicating the frequency-domain componentsand a set of linear combination coefficients. The network nodecomprises: a receiver; a transmitter; and processing circuitry coupledto the receiver and the transmitter. The processing circuitry isconfigured to receive, from a wireless device, the CSI report comprisingan indication of a second set of candidate frequency-domain componentsbeing a subset of a first set of candidate frequency-domain components;one or more spatial-domain component-specific sets of frequency-domaincomponents being subsets of the second set of candidate frequency-domaincomponents, each frequency-domain component in the one or morespatial-domain component-specific sets of frequency-domain componentsbeing associated with non-zero coefficients of the set of linearcombination coefficients; and the non-zero coefficients. The processingcircuitry is configured to determine one or more precoder vectors basedupon the indication received in the CSI report.

In certain embodiments, the processing circuitry may be furtherconfigured to use one of the determined one or more precoder vectors toperform a transmission to the wireless device.

In certain embodiments, the processing circuitry may be furtherconfigured to use a different precoder vector from the one or moredetermined precoder vectors to perform a transmission to the wirelessdevice.

In certain embodiments, a size of the frequency sub-band may be aninteger number of PRBs.

Certain embodiments of the present disclosure may provide one or moretechnical advantages. As one example, certain embodiments mayadvantageously increase MU-MIMO performance by having rich precoderfeedback with reasonable feedback overhead. As another example, incertain embodiments the performance/overhead trade-off can be furtheroptimized by allowing the frequency-domain basis vectors for each beamto be independently selected from a smaller subset of common basis beam,which advantageously reduces their index space. Other advantages may bereadily apparent to one having skill in the art. Certain embodiments mayhave none, some, or all of the recited advantages.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the disclosed embodiments and theirfeatures and advantages, reference is now made to the followingdescription, taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 illustrates a transmission structure of precoded spatialmultiplexing mode in NR, in accordance with certain embodiments;

FIG. 2 illustrates a two-dimensional antenna array of cross-polarizedantenna elements, in accordance with certain embodiments;

FIG. 3 illustrates an example of resource element allocation for a12-port CSI-RS in NR, in accordance with certain embodiments;

FIG. 4 illustrates a matrix representation of the Type II overheadreduction scheme, in accordance with certain embodiments;

FIG. 5 illustrates an example wireless network, in accordance withcertain embodiments;

FIG. 6 is a flowchart illustrating an example of a method performed by awireless device, in accordance with certain embodiments;

FIG. 7 is a block diagram illustrating an example of a virtualapparatus, in accordance with certain embodiments;

FIG. 8 is a flowchart illustrating an example of a method performed by anetwork node, in accordance with certain embodiments;

FIG. 9 is a block diagram illustrating an example of a virtualapparatus, in accordance with certain embodiments.

FIG. 10 illustrates an example user equipment, in accordance withcertain embodiments;

FIG. 11 illustrates an example virtualization environment, in accordancewith certain embodiments;

FIG. 12 illustrates an example telecommunication network connected viaan intermediate network to a host computer, in accordance with certainembodiments;

FIG. 13 illustrates an example host computer communicating via a basestation with a user equipment over a partially wireless connection, inaccordance with certain embodiments;

FIG. 14 is a flowchart illustrating an example method implemented in acommunication system, in accordance certain embodiments;

FIG. 15 is a flowchart illustrating a second example method implementedin a communication system, in accordance with certain embodiments;

FIG. 16 is a flowchart illustrating a third method implemented in acommunication system, in accordance with certain embodiments; and

FIG. 17 is a flowchart illustrating a fourth method implemented in acommunication system, in accordance with certain embodiments.

DETAILED DESCRIPTION

Generally, all terms used herein are to be interpreted according totheir ordinary meaning in the relevant technical field, unless adifferent meaning is clearly given and/or is implied from the context inwhich it is used. All references to a/an/the element, apparatus,component, means, step, etc. are to be interpreted openly as referringto at least one instance of the element, apparatus, component, means,step, etc., unless explicitly stated otherwise. The steps of any methodsdisclosed herein do not have to be performed in the exact orderdisclosed, unless a step is explicitly described as following orpreceding another step and/or where it is implicit that a step mustfollow or precede another step. Any feature of any of the embodimentsdisclosed herein may be applied to any other embodiment, whereverappropriate. Likewise, any advantage of any of the embodiments may applyto any other embodiments, and vice versa. Other objectives, features andadvantages of the enclosed embodiments will be apparent from thefollowing description.

As described above, with MU-MIMO, two or more users in the same cell canbe co-scheduled on the same time-frequency resource. Because one centralpart of MU-MIMO is obtaining accurate CSI that enables nullformingbetween co-scheduled users, support has been added in LTE Rel-14 and NRRel-15 for codebooks that provide more detailed CSI than the traditionalsingle DFT-beam precoders. These codebooks are referred to as AdvancedCSI (in LTE) or Type II codebooks (in NR). Although Type II precoderschemes may lead to better MU-MIMO performance, Type II precoder schemesare problematic due to increased CSI feedback overhead and UE precodersearch complexity. Thus, there is a need for an efficient Type IIcodebook that results in good MU-MIMO performance and low feedbackoverhead as well as an improved method for deriving the CSI feedback bythe UE. Moreover, there is a need to support higher rank representationsfor Type II feedback. This is problematic, as feedback overheadincreases with the number of layers, which makes a high layerrepresentation infeasible.

Certain aspects of the present disclosure and the embodiments describedherein may provide solutions to these or other challenges. According toone example embodiment, a method performed by a wireless device fortransmitting a CSI report for a DL channel is disclosed. The CSI reportindicates a plurality of precoder vectors. Each of the precoder vectorscorresponds to a frequency sub-band of the bandwidth of the DL channel.A precoder vector may be expressed as a linear combination ofspatial-domain components and frequency-domain components. Indicatingthe plurality of precoder vectors may comprise indicating thefrequency-domain components and a set of linear combinationcoefficients.

In this example embodiment, the wireless device (e.g., a UE) obtains afirst set of candidate frequency-domain components and determines a setof spatial-domain components. The wireless device determines a secondset of candidate frequency-domain components as a subset of the firstset of candidate frequency-domain components. The wireless devicedetermines, for each spatial-domain component of the set ofspatial-domain components, a spatial-domain component-specific set offrequency-domain components as a subset of the second set of candidatefrequency-domain components. Each frequency-domain component in thespatial-domain component-specific set of frequency-domain components maybe associated with a non-zero coefficient of the set of linearcombination coefficients. The wireless device transmits, to a networknode (e.g., a gNB), the CSI report comprising an indication of: thedetermined second set of candidate frequency-domain components; thedetermined spatial-domain component-specific sets of frequency-domaincomponents; and the non-zero coefficients of the set of linearcombination coefficients.

According to other example embodiments, a corresponding wireless device,computer program, and computer program product are also disclosed.

According to another example embodiment, a method performed by a networknode for receiving a CSI report for a DL channel is disclosed. The CSIreport indicates a plurality of precoder vectors. Each of the precodervectors corresponds to a frequency sub-band of the bandwidth of the DLchannel A precoder vector may be expressed as a linear combination ofspatial-domain components and frequency-domain components, and theplurality of precoder vectors may be indicated by indicating thefrequency-domain components and a set of linear combinationcoefficients.

The network node receives, from a wireless device, the CSI reportcomprising an indication of: a second set of candidate frequency-domaincomponents being a subset of a first set of candidate frequency-domaincomponents; one or more spatial-domain component-specific sets offrequency-domain components being subsets of the second set of candidatefrequency-domain components, each frequency-domain component in the oneor more spatial-domain component-specific sets of frequency-domaincomponents being associated with non-zero coefficients of the set oflinear combination coefficients; and the non-zero coefficients. Thenetwork node determines one or more precoder vectors based upon theindication received in the CSI report.

According to other example embodiments, a corresponding network node,computer program, and computer program product are also disclosed.

Some of the embodiments contemplated herein will now be described morefully with reference to the accompanying drawings. Other embodiments,however, are contained within the scope of the subject matter disclosedherein, the disclosed subject matter should not be construed as limitedto only the embodiments set forth herein; rather, these embodiments areprovided by way of example to convey the scope of the subject matter tothose skilled in the art.

FIG. 5 illustrates a wireless network in accordance with someembodiments. Although the subject matter described herein may beimplemented in any appropriate type of system using any suitablecomponents, the embodiments disclosed herein are described in relationto a wireless network, such as the example wireless network illustratedin FIG. 5. For simplicity, the wireless network of FIG. 5 only depictsnetwork 506, network nodes 560 and 560 b, and wireless devices 510, 510b, and 510 c. In practice, a wireless network may further include anyadditional elements suitable to support communication between wirelessdevices or between a wireless device and another communication device,such as a landline telephone, a service provider, or any other networknode or end device. Of the illustrated components, network node 560 andwireless device 510 are depicted with additional detail. The wirelessnetwork may provide communication and other types of services to one ormore wireless devices to facilitate the wireless devices' access toand/or use of the services provided by, or via, the wireless network.

The wireless network may comprise and/or interface with any type ofcommunication, telecommunication, data, cellular, and/or radio networkor other similar type of system. In some embodiments, the wirelessnetwork may be configured to operate according to specific standards orother types of predefined rules or procedures. Thus, particularembodiments of the wireless network may implement communicationstandards, such as Global System for Mobile Communications (GSM),Universal Mobile Telecommunications System (UMTS), Long Term Evolution(LTE), and/or other suitable 2G, 3G, 4G, or 5G standards; wireless localarea network (WLAN) standards, such as the IEEE 802.11 standards; and/orany other appropriate wireless communication standard, such as theWorldwide Interoperability for Microwave Access (WiMax), Bluetooth,Z-Wave and/or ZigBee standards.

Network 506 may comprise one or more backhaul networks, core networks,IP networks, public switched telephone networks (PSTNs), packet datanetworks, optical networks, wide-area networks (WANs), local areanetworks (LANs), wireless local area networks (WLANs), wired networks,wireless networks, metropolitan area networks, and other networks toenable communication between devices.

Network node 560 and wireless device 510 comprise various componentsdescribed in more detail below. These components work together in orderto provide network node and/or wireless device functionality, such asproviding wireless connections in a wireless network. In differentembodiments, the wireless network may comprise any number of wired orwireless networks, network nodes, base stations, controllers, wirelessdevices, relay stations, and/or any other components or systems that mayfacilitate or participate in the communication of data and/or signalswhether via wired or wireless connections.

As used herein, network node refers to equipment capable, configured,arranged and/or operable to communicate directly or indirectly with awireless device and/or with other network nodes or equipment in thewireless network to enable and/or provide wireless access to thewireless device and/or to perform other functions (e.g., administration)in the wireless network. Examples of network nodes include, but are notlimited to, access points (APs) (e.g., radio access points), basestations (BSs) (e.g., radio base stations, Node Bs, evolved Node Bs(eNBs) and NR NodeBs (gNBs)). Base stations may be categorized based onthe amount of coverage they provide (or, stated differently, theirtransmit power level) and may then also be referred to as femto basestations, pico base stations, micro base stations, or macro basestations. A base station may be a relay node or a relay donor nodecontrolling a relay. A network node may also include one or more (orall) parts of a distributed radio base station such as centralizeddigital units and/or remote radio units (RRUs), sometimes referred to asRemote Radio Heads (RRHs). Such remote radio units may or may not beintegrated with an antenna as an antenna integrated radio. Parts of adistributed radio base station may also be referred to as nodes in adistributed antenna system (DAS). Yet further examples of network nodesinclude multi-standard radio (MSR) equipment such as MSR BSs, networkcontrollers such as radio network controllers (RNCs) or base stationcontrollers (BSCs), base transceiver stations (BTSs), transmissionpoints, transmission nodes, multi-cell/multicast coordination entities(MCEs), core network nodes (e.g., MSCs, MMEs), O&M nodes, OSS nodes, SONnodes, positioning nodes (e.g., E-SMLCs), and/or MDTs. As anotherexample, a network node may be a virtual network node as described inmore detail below. More generally, however, network nodes may representany suitable device (or group of devices) capable, configured, arranged,and/or operable to enable and/or provide a wireless device with accessto the wireless network or to provide some service to a wireless devicethat has accessed the wireless network.

In FIG. 5, network node 560 includes processing circuitry 570, devicereadable medium 580, interface 590, auxiliary equipment 584, powersource 586, power circuitry 587, and antenna 562. Although network node560 illustrated in the example wireless network of FIG. 5 may representa device that includes the illustrated combination of hardwarecomponents, other embodiments may comprise network nodes with differentcombinations of components. It is to be understood that a network nodecomprises any suitable combination of hardware and/or software needed toperform the tasks, features, functions and methods disclosed herein.Moreover, while the components of network node 560 are depicted assingle boxes located within a larger box, or nested within multipleboxes, in practice, a network node may comprise multiple differentphysical components that make up a single illustrated component (e.g.,device readable medium 580 may comprise multiple separate hard drives aswell as multiple RAM modules).

Similarly, network node 560 may be composed of multiple physicallyseparate components (e.g., a NodeB component and a RNC component, or aBTS component and a BSC component, etc.), which may each have their ownrespective components. In certain scenarios in which network node 560comprises multiple separate components (e.g., BTS and BSC components),one or more of the separate components may be shared among severalnetwork nodes. For example, a single RNC may control multiple NodeB's.In such a scenario, each unique NodeB and RNC pair, may in someinstances be considered a single separate network node. In someembodiments, network node 560 may be configured to support multipleradio access technologies (RATs). In such embodiments, some componentsmay be duplicated (e.g., separate device readable medium 580 for thedifferent RATs) and some components may be reused (e.g., the sameantenna 562 may be shared by the RATs). Network node 560 may alsoinclude multiple sets of the various illustrated components fordifferent wireless technologies integrated into network node 560, suchas, for example, GSM, WCDMA, LTE, NR, WiFi, or Bluetooth wirelesstechnologies. These wireless technologies may be integrated into thesame or different chip or set of chips and other components withinnetwork node 560.

Processing circuitry 570 is configured to perform any determining,calculating, or similar operations (e.g., certain obtaining operations)described herein as being provided by a network node. These operationsperformed by processing circuitry 570 may include processing informationobtained by processing circuitry 570 by, for example, converting theobtained information into other information, comparing the obtainedinformation or converted information to information stored in thenetwork node, and/or performing one or more operations based on theobtained information or converted information, and as a result of saidprocessing making a determination.

Processing circuitry 570 may comprise a combination of one or more of amicroprocessor, controller, microcontroller, central processing unit,digital signal processor, application-specific integrated circuit, fieldprogrammable gate array, or any other suitable computing device,resource, or combination of hardware, software and/or encoded logicoperable to provide, either alone or in conjunction with other networknode 560 components, such as device readable medium 580, network node560 functionality. For example, processing circuitry 570 may executeinstructions stored in device readable medium 580 or in memory withinprocessing circuitry 570. Such functionality may include providing anyof the various wireless features, functions, or benefits discussedherein. In some embodiments, processing circuitry 570 may include asystem on a chip (SOC).

In some embodiments, processing circuitry 570 may include one or more ofradio frequency (RF) transceiver circuitry 572 and baseband processingcircuitry 574. In some embodiments, radio frequency (RF) transceivercircuitry 572 and baseband processing circuitry 574 may be on separatechips (or sets of chips), boards, or units, such as radio units anddigital units. In alternative embodiments, part or all of RF transceivercircuitry 572 and baseband processing circuitry 574 may be on the samechip or set of chips, boards, or units

In certain embodiments, some or all of the functionality describedherein as being provided by a network node, base station, eNB or othersuch network device may be performed by processing circuitry 570executing instructions stored on device readable medium 580 or memorywithin processing circuitry 570. In alternative embodiments, some or allof the functionality may be provided by processing circuitry 570 withoutexecuting instructions stored on a separate or discrete device readablemedium, such as in a hard-wired manner. In any of those embodiments,whether executing instructions stored on a device readable storagemedium or not, processing circuitry 570 can be configured to perform thedescribed functionality. The benefits provided by such functionality arenot limited to processing circuitry 570 alone or to other components ofnetwork node 560, but are enjoyed by network node 560 as a whole, and/orby end users and the wireless network generally.

Device readable medium 580 may comprise any form of volatile ornon-volatile computer readable memory including, without limitation,persistent storage, solid-state memory, remotely mounted memory,magnetic media, optical media, random access memory (RAM), read-onlymemory (ROM), mass storage media (for example, a hard disk), removablestorage media (for example, a flash drive, a Compact Disk (CD) or aDigital Video Disk (DVD)), and/or any other volatile or non-volatile,non-transitory device readable and/or computer-executable memory devicesthat store information, data, and/or instructions that may be used byprocessing circuitry 570. Device readable medium 580 may store anysuitable instructions, data or information, including a computerprogram, software, an application including one or more of logic, rules,code, tables, etc. and/or other instructions capable of being executedby processing circuitry 570 and, utilized by network node 560. Devicereadable medium 580 may be used to store any calculations made byprocessing circuitry 570 and/or any data received via interface 590. Insome embodiments, processing circuitry 570 and device readable medium580 may be considered to be integrated.

Interface 590 is used in the wired or wireless communication ofsignalling and/or data between network node 560, network 506, and/orwireless devices 510. As illustrated, interface 590 comprisesport(s)/terminal(s) 594 to send and receive data, for example to andfrom network 506 over a wired connection. Interface 590 also includesradio front end circuitry 592 that may be coupled to, or in certainembodiments a part of, antenna 562. Radio front end circuitry 592comprises filters 598 and amplifiers 596. Radio front end circuitry 592may be connected to antenna 562 and processing circuitry 570. Radiofront end circuitry may be configured to condition signals communicatedbetween antenna 562 and processing circuitry 570. Radio front endcircuitry 592 may receive digital data that is to be sent out to othernetwork nodes or wireless devices via a wireless connection. Radio frontend circuitry 592 may convert the digital data into a radio signalhaving the appropriate channel and bandwidth parameters using acombination of filters 598 and/or amplifiers 596. The radio signal maythen be transmitted via antenna 562. Similarly, when receiving data,antenna 562 may collect radio signals which are then converted intodigital data by radio front end circuitry 592. The digital data may bepassed to processing circuitry 570. In other embodiments, the interfacemay comprise different components and/or different combinations ofcomponents.

In certain alternative embodiments, network node 560 may not includeseparate radio front end circuitry 592, instead, processing circuitry570 may comprise radio front end circuitry and may be connected toantenna 562 without separate radio front end circuitry 592. Similarly,in some embodiments, all or some of RF transceiver circuitry 572 may beconsidered a part of interface 590. In still other embodiments,interface 590 may include one or more ports or terminals 594, radiofront end circuitry 592, and RF transceiver circuitry 572, as part of aradio unit (not shown), and interface 590 may communicate with basebandprocessing circuitry 574, which is part of a digital unit (not shown).

Antenna 562 may include one or more antennas, or antenna arrays,configured to send and/or receive wireless signals. Antenna 562 may becoupled to radio front end circuitry 590 and may be any type of antennacapable of transmitting and receiving data and/or signals wirelessly. Insome embodiments, antenna 562 may comprise one or more omni-directional,sector or panel antennas operable to transmit/receive radio signalsbetween, for example, 2 GHz and 66 GHz. An omni-directional antenna maybe used to transmit/receive radio signals in any direction, a sectorantenna may be used to transmit/receive radio signals from deviceswithin a particular area, and a panel antenna may be a line of sightantenna used to transmit/receive radio signals in a relatively straightline. In some instances, the use of more than one antenna may bereferred to as MIMO. In certain embodiments, antenna 562 may be separatefrom network node 560 and may be connectable to network node 560 throughan interface or port. Certain embodiments of the present disclosure maybe used with two-dimensional antenna arrays.

Antenna 562, interface 590, and/or processing circuitry 570 may beconfigured to perform any receiving operations and/or certain obtainingoperations described herein as being performed by a network node. Anyinformation, data and/or signals may be received from a wireless device,another network node and/or any other network equipment. Similarly,antenna 562, interface 590, and/or processing circuitry 570 may beconfigured to perform any transmitting operations described herein asbeing performed by a network node. Any information, data and/or signalsmay be transmitted to a wireless device, another network node and/or anyother network equipment.

Power circuitry 587 may comprise, or be coupled to, power managementcircuitry and is configured to supply the components of network node 560with power for performing the functionality described herein. Powercircuitry 587 may receive power from power source 586. Power source 586and/or power circuitry 587 may be configured to provide power to thevarious components of network node 560 in a form suitable for therespective components (e.g., at a voltage and current level needed foreach respective component). Power source 586 may either be included in,or external to, power circuitry 587 and/or network node 560. Forexample, network node 560 may be connectable to an external power source(e.g., an electricity outlet) via an input circuitry or interface suchas an electrical cable, whereby the external power source supplies powerto power circuitry 587. As a further example, power source 586 maycomprise a source of power in the form of a battery or battery packwhich is connected to, or integrated in, power circuitry 587. Thebattery may provide backup power should the external power source fail.Other types of power sources, such as photovoltaic devices, may also beused.

Alternative embodiments of network node 560 may include additionalcomponents beyond those shown in FIG. 5 that may be responsible forproviding certain aspects of the network node's functionality, includingany of the functionality described herein and/or any functionalitynecessary to support the subject matter described herein. For example,network node 560 may include user interface equipment to allow input ofinformation into network node 560 and to allow output of informationfrom network node 560. This may allow a user to perform diagnostic,maintenance, repair, and other administrative functions for network node560.

As used herein, wireless device refers to a device capable, configured,arranged and/or operable to communicate wirelessly with network nodesand/or other wireless devices. Unless otherwise noted, the term wirelessdevice may be used interchangeably herein with user equipment (UE).Communicating wirelessly may involve transmitting and/or receivingwireless signals using electromagnetic waves, radio waves, infraredwaves, and/or other types of signals suitable for conveying informationthrough air. In some embodiments, a wireless device may be configured totransmit and/or receive information without direct human interaction.For instance, a wireless device may be designed to transmit informationto a network on a predetermined schedule, when triggered by an internalor external event, or in response to requests from the network. Examplesof a wireless device include, but are not limited to, a smart phone, amobile phone, a cell phone, a voice over IP (VoIP) phone, a wirelesslocal loop phone, a desktop computer, a personal digital assistant(PDA), a wireless cameras, a gaming console or device, a music storagedevice, a playback appliance, a wearable terminal device, a wirelessendpoint, a mobile station, a tablet, a laptop, a laptop-embeddedequipment (LEE), a laptop-mounted equipment (LME), a smart device, awireless customer-premise equipment (CPE), a vehicle-mounted wirelessterminal device, etc. A wireless device may support device-to-device(D2D) communication, for example by implementing a 3GPP standard forsidelink communication, vehicle-to-vehicle (V2V),vehicle-to-infrastructure (V2I), vehicle-to-everything (V2X) and may inthis case be referred to as a D2D communication device. As yet anotherspecific example, in an Internet of Things (IoT) scenario, a wirelessdevice may represent a machine or other device that performs monitoringand/or measurements, and transmits the results of such monitoring and/ormeasurements to another wireless device and/or a network node. Thewireless device may in this case be a machine-to-machine (M2M) device,which may in a 3GPP context be referred to as an MTC device. As oneparticular example, the wireless device may be a UE implementing the3GPP narrow band internet of things (NB-IoT) standard. Particularexamples of such machines or devices are sensors, metering devices suchas power meters, industrial machinery, or home or personal appliances(e.g. refrigerators, televisions, etc.) personal wearables (e.g.,watches, fitness trackers, etc.). In other scenarios, a wireless devicemay represent a vehicle or other equipment that is capable of monitoringand/or reporting on its operational status or other functions associatedwith its operation. A wireless device as described above may representthe endpoint of a wireless connection, in which case the device may bereferred to as a wireless terminal. Furthermore, a wireless device asdescribed above may be mobile, in which case it may also be referred toas a mobile device or a mobile terminal.

As illustrated, wireless device 510 includes antenna 511, interface 514,processing circuitry 520, device readable medium 530, user interfaceequipment 532, auxiliary equipment 534, power source 536 and powercircuitry 537. Wireless device 510 may include multiple sets of one ormore of the illustrated components for different wireless technologiessupported by wireless device 510, such as, for example, GSM, WCDMA, LTE,NR, WiFi, WiMAX, or Bluetooth wireless technologies, just to mention afew. These wireless technologies may be integrated into the same ordifferent chips or set of chips as other components within wirelessdevice 510.

Antenna 511 may include one or more antennas or antenna arrays,configured to send and/or receive wireless signals, and is connected tointerface 514. In certain alternative embodiments, antenna 511 may beseparate from wireless device 510 and be connectable to wireless device510 through an interface or port. Antenna 511, interface 514, and/orprocessing circuitry 520 may be configured to perform any receiving ortransmitting operations described herein as being performed by awireless device. Any information, data and/or signals may be receivedfrom a network node and/or another wireless device. In some embodiments,radio front end circuitry and/or antenna 511 may be considered aninterface. Certain embodiments of the present disclosure may be usedwith two-dimensional antenna arrays.

As illustrated, interface 514 comprises radio front end circuitry 512and antenna 511. Radio front end circuitry 512 comprise one or morefilters 518 and amplifiers 516. Radio front end circuitry 514 isconnected to antenna 511 and processing circuitry 520, and is configuredto condition signals communicated between antenna 511 and processingcircuitry 520. Radio front end circuitry 512 may be coupled to or a partof antenna 511. In some embodiments, wireless device 510 may not includeseparate radio front end circuitry 512; rather, processing circuitry 520may comprise radio front end circuitry and may be connected to antenna511. Similarly, in some embodiments, some or all of RF transceivercircuitry 522 may be considered a part of interface 514. Radio front endcircuitry 512 may receive digital data that is to be sent out to othernetwork nodes or wireless devices via a wireless connection. Radio frontend circuitry 512 may convert the digital data into a radio signalhaving the appropriate channel and bandwidth parameters using acombination of filters 518 and/or amplifiers 516. The radio signal maythen be transmitted via antenna 511. Similarly, when receiving data,antenna 511 may collect radio signals which are then converted intodigital data by radio front end circuitry 512. The digital data may bepassed to processing circuitry 520. In other embodiments, the interfacemay comprise different components and/or different combinations ofcomponents.

Processing circuitry 520 may comprise a combination of one or more of amicroprocessor, controller, microcontroller, central processing unit,digital signal processor, application-specific integrated circuit, fieldprogrammable gate array, or any other suitable computing device,resource, or combination of hardware, software, and/or encoded logicoperable to provide, either alone or in conjunction with other wirelessdevice 510 components, such as device readable medium 530, wirelessdevice 510 functionality. Such functionality may include providing anyof the various wireless features or benefits discussed herein. Forexample, processing circuitry 520 may execute instructions stored indevice readable medium 530 or in memory within processing circuitry 520to provide the functionality disclosed herein.

As illustrated, processing circuitry 520 includes one or more of RFtransceiver circuitry 522, baseband processing circuitry 524, andapplication processing circuitry 526. In other embodiments, theprocessing circuitry may comprise different components and/or differentcombinations of components. In certain embodiments processing circuitry520 of wireless device 510 may comprise a SOC. In some embodiments, RFtransceiver circuitry 522, baseband processing circuitry 524, andapplication processing circuitry 526 may be on separate chips or sets ofchips. In alternative embodiments, part or all of baseband processingcircuitry 524 and application processing circuitry 526 may be combinedinto one chip or set of chips, and RF transceiver circuitry 522 may beon a separate chip or set of chips. In still alternative embodiments,part or all of RF transceiver circuitry 522 and baseband processingcircuitry 524 may be on the same chip or set of chips, and applicationprocessing circuitry 526 may be on a separate chip or set of chips. Inyet other alternative embodiments, part or all of RF transceivercircuitry 522, baseband processing circuitry 524, and applicationprocessing circuitry 526 may be combined in the same chip or set ofchips. In some embodiments, RF transceiver circuitry 522 may be a partof interface 514. RF transceiver circuitry 522 may condition RF signalsfor processing circuitry 520.

In certain embodiments, some or all of the functionality describedherein as being performed by a wireless device may be provided byprocessing circuitry 520 executing instructions stored on devicereadable medium 530, which in certain embodiments may be acomputer-readable storage medium. In alternative embodiments, some orall of the functionality may be provided by processing circuitry 520without executing instructions stored on a separate or discrete devicereadable storage medium, such as in a hard-wired manner. In any of thoseparticular embodiments, whether executing instructions stored on adevice readable storage medium or not, processing circuitry 520 can beconfigured to perform the described functionality. The benefits providedby such functionality are not limited to processing circuitry 520 aloneor to other components of wireless device 510, but are enjoyed bywireless device 510 as a whole, and/or by end users and the wirelessnetwork generally.

Processing circuitry 520 may be configured to perform any determining,calculating, or similar operations (e.g., certain obtaining operations)described herein as being performed by a wireless device. Theseoperations, as performed by processing circuitry 520, may includeprocessing information obtained by processing circuitry 520 by, forexample, converting the obtained information into other information,comparing the obtained information or converted information toinformation stored by wireless device 510, and/or performing one or moreoperations based on the obtained information or converted information,and as a result of said processing making a determination Devicereadable medium 530 may be operable to store a computer program,software, an application including one or more of logic, rules, code,tables, etc. and/or other instructions capable of being executed byprocessing circuitry 520. Device readable medium 530 may includecomputer memory (e.g., Random Access Memory (RAM) or Read Only Memory(ROM)), mass storage media (e.g., a hard disk), removable storage media(e.g., a Compact Disk (CD) or a Digital Video Disk (DVD)), and/or anyother volatile or non-volatile, non-transitory device readable and/orcomputer executable memory devices that store information, data, and/orinstructions that may be used by processing circuitry 520. In someembodiments, processing circuitry 520 and device readable medium 530 maybe considered to be integrated.

User interface equipment 532 may provide components that allow for ahuman user to interact with wireless device 510. Such interaction may beof many forms, such as visual, audial, tactile, etc. User interfaceequipment 532 may be operable to produce output to the user and to allowthe user to provide input to wireless device 510. The type ofinteraction may vary depending on the type of user interface equipment532 installed in wireless device 510. For example, if wireless device510 is a smart phone, the interaction may be via a touch screen; ifwireless device 510 is a smart meter, the interaction may be through ascreen that provides usage (e.g., the number of gallons used) or aspeaker that provides an audible alert (e.g., if smoke is detected).User interface equipment 532 may include input interfaces, devices andcircuits, and output interfaces, devices and circuits. User interfaceequipment 532 is configured to allow input of information into wirelessdevice 510, and is connected to processing circuitry 520 to allowprocessing circuitry 520 to process the input information. Userinterface equipment 532 may include, for example, a microphone, aproximity or other sensor, keys/buttons, a touch display, one or morecameras, a USB port, or other input circuitry. User interface equipment532 is also configured to allow output of information from wirelessdevice 510, and to allow processing circuitry 520 to output informationfrom wireless device 510. User interface equipment 532 may include, forexample, a speaker, a display, vibrating circuitry, a USB port, aheadphone interface, or other output circuitry Using one or more inputand output interfaces, devices, and circuits, of user interfaceequipment 532, wireless device 510 may communicate with end users and/orthe wireless network, and allow them to benefit from the functionalitydescribed herein.

Auxiliary equipment 534 is operable to provide more specificfunctionality which may not be generally performed by wireless devices.This may comprise specialized sensors for doing measurements for variouspurposes, interfaces for additional types of communication such as wiredcommunications etc. The inclusion and type of components of auxiliaryequipment 534 may vary depending on the embodiment and/or scenario.

Power source 536 may, in some embodiments, be in the form of a batteryor battery pack. Other types of power sources, such as an external powersource (e.g., an electricity outlet), photovoltaic devices or powercells, may also be used. Wireless device 510 may further comprise powercircuitry 537 for delivering power from power source 536 to the variousparts of wireless device 510 which need power from power source 536 tocarry out any functionality described or indicated herein. Powercircuitry 537 may in certain embodiments comprise power managementcircuitry. Power circuitry 537 may additionally or alternatively beoperable to receive power from an external power source; in which casewireless device 510 may be connectable to the external power source(such as an electricity outlet) via input circuitry or an interface suchas an electrical power cable. Power circuitry 537 may also in certainembodiments be operable to deliver power from an external power sourceto power source 536. This may be, for example, for the charging of powersource 536. Power circuitry 537 may perform any formatting, converting,or other modification to the power from power source 536 to make thepower suitable for the respective components of wireless device 510 towhich power is supplied.

For a radio propagation channel, there are typically a few distinctpropagation paths over which a transmitted signal will propagate. Thesedifferent paths will typically constitute different spatial directions,path loss and delay. When multi-beam precoders are applied to such achannel, it may be that for a given beam some of the propagation pathsare clearly visible whereas some others are suppressed (e.g., due to thebeam's beamforming gain varying with spatial direction). The existingpropagation paths, however, are a consequence of the physicalenvironment and hence common for all beams.

Certain embodiments of the present disclosure utilize this observationby creating a basis common for all beams which, at least partly,captures the propagation characteristics of the channel in the frequencydomain. Hence, this basis is a representation of, potentially, all thepropagation paths of the channel and its size is typically much smallerthan if the entire channel space were described. Based on this commonbasis, a beam-specific selection can be performed, to describe thedominant components within each beam. The channel can then be described,for a given beam, as a combination of these selected beams.

To illustrate, assume that there are K PRBs and it is desired torepresent c_(l,i)(k) over these PRBs. In such a scenario, the steps canbe generally described as follows: creating a first basis constituting Kvectors spanning the K-dimensional space

^(K); from this first basis, selecting Kc<K vectors that are used tocreate a second basis, referred to as the common basis above, spanning asubset of the K-dimensional space

^(L); for each beam, selecting Kb<=Kc vectors from the second basis; andfor each beam, representing c_(l,i) as a linear combination of the Kbbeams selected from the second basis.

More particularly, according to one example embodiment a wireless device(e.g., a UE), such as wireless device 510, may perform a method fortransmitting a CSI report for a DL channel (e.g., to a network node,such as network node 560). The CSI report may indicate a plurality ofprecoder vectors. Each of the precoder vectors may correspond to afrequency sub-band of the bandwidth of the DL channel. In certainembodiments, a size of the frequency sub-band may be an integer numberof PRBs. A precoder vector may be expressed as a linear combination ofspatial-domain components and frequency-domain components. The pluralityof precoder vectors may be indicated by indicating the frequency-domaincomponents and a set of linear combination coefficients. In order totransmit the CSI report for the DL channel, wireless device 510 mayperform the following steps, or a subset thereof.

According to this example embodiment, in a first step wireless device510 obtains a first set of candidate frequency-domain components. Afrequency-domain component may correspond to a basis vector and a set offrequency-domain components may correspond to a basis. In certainembodiments, the candidate frequency-domain components may be orthogonalbasis vectors. In certain embodiments, the orthogonal basis vectors maybe discrete Fourier transform vectors. As described in more detailbelow, as part of obtaining the first set of candidate frequency-domaincomponents, wireless device 510 may define a first basis constituting anumber of basis vectors. For example, in certain embodiments the firstset of candidate frequency-domain components may be a first basis matrixB comprising K basis vectors.

To further illustrate this step, assume that there are Kfrequency-domain sub-bands, whereon it is desired to representc_(l,i)(k), and that the size of the frequency sub-band may for instancebe one PRB, or a number of PRBs, and may or may not relate to some otherconfigured quantity. In this step, wireless device 510 obtains a firstset of candidate frequency-domain components (i.e., a first basis, whichin one example is for the entire channel space). In certain embodiments,the first basis constituting a number of basis vectors spanning theK-dimensional space

^(K) may be defined. This basis could, for instance, be a DFT matrixcreated by concatenating a set of DFT beams:w _(1D)(j) for j=0,1, . . . Q _(ƒ) K−1,where Q_(ƒ) is an oversampling factor. In certain embodiments, the basismay be described by:B=[w _(1D)(0)w _(1D)(1) . . . w _(1D)(Q _(ƒ) K−1)],implying that there are Q_(ƒ)K vectors in the basis. Such a basis isknown as an oversampled DFT basis.

In some cases, it may be desirable to work with an orthogonal DFT basisrather than an oversampled DFT basis. In such cases, an orthogonal DFTbasis may be obtained by selecting the DFT vectors with indicessatisfying i=Q_(ƒ)k+q, k=0, . . . , K−1 for some value of q=0, . . . ,Q_(ƒ)−1. The parameter q is known as a rotation factor and a basisobtained for different values of q are known as a rotated DFT basis.

Thus, in certain embodiments, the first set of candidatefrequency-domain components may correspond to an oversampled DFT basis.In other embodiments, the first set of candidate frequency-domaincomponents may correspond to an orthogonal DFT basis (i.e., that thebasis comprises K orthogonal DFT vectors of length K). In some suchembodiments, the orthogonal DFT basis may be obtained as a rotated DFTbasis by determining a rotation factor q. In other such embodiments, anoversampling factor of Q_(ƒ)=1 may be used, which may imply that thebasis is fixed in a specification.

In certain embodiments, alternative structures may be used for creatingthe basis, such as Discrete Cosine Transform (DCT) vectors.

The present disclosure contemplates that wireless device 510 may obtainthe first set of candidate frequency-domain components in a variety ofways, and that the manner in which wireless device 510 obtains the firstset of candidate frequency-domain components may vary in differentimplementations. As one example, wireless device 510 may obtain thefirst set of candidate frequency-domain components by accessing apredefined table (e.g., a predefined table in the specification). Asanother example, wireless device 510 may obtain the first set ofcandidate frequency-domain components via higher layer signaling. Asstill another example, wireless device 510 may obtain the first set ofcandidate frequency-domain components by determining the first set ofcandidate frequency-domain components.

For instance, the first set of candidate frequency-domain components maycorrespond to either the full frequency-domain basis (which may be usedwhen the bandwidth is small) or a rank-common frequency-domain basissubset (which may be used when the bandwidth is large). In certainembodiments, if the first set of candidate frequency-domain componentscorresponds to the full frequency-domain basis, the first set ofcandidate frequency-domain components may be fixed (e.g., in thespecification) and hence may not be determined by wireless device 510.Rather, in such a scenario wireless device 510 may obtain the first setof candidate frequency-domain components by accessing a predefined tableor via higher layer signaling. In certain embodiments, if the first setof candidate frequency-domain components corresponds to the intermediaryrank-common frequency-domain basis subset, wireless device 510 maydetermine the first set of candidate frequency-domain components.

In certain embodiments, K may be specified in the standard. In certainembodiments, K may be configurable. In certain embodiments, K may berank dependent and may be thus be expressed as K(r), where r is therank. In certain embodiments, B may be rank dependent and written B(r).In one such embodiment, B(r2) may comprises fewer columns than B(r1)when r2>r1.

In a second step, wireless device 510 determines a set of spatial-domaincomponents. In certain embodiments, the set of spatial-domain componentsmay correspond to the L beams, which are determined by wireless device510.

In the third step, wireless device 510 determines a second set ofcandidate frequency-domain components as a subset of the first set ofcandidate frequency-domain components. In this step, a subset of thefirst set of candidate frequency-domain components may be selected bywireless device 510 to form a second set of candidate frequency-domaincomponents (i.e., create a common basis for all beams or spatial-domaincomponents). In certain embodiments, wireless device 510 may analyze anestimate of the DL channel to determine one or more properties of the DLchannel and select the second set of candidate frequency-domaincomponents from the first set of candidate frequency-domain componentsbased on the determined one or more properties of the DL channel.

As described in more detail below, in certain embodiments, indetermining the second set of candidate frequency-domain components as asubset of the first set of candidate frequency-domain components,wireless device 510 may create a common basis for all spatial-domaincomponents. For example, wireless device 510 may select K_(c)<K columnsof the first basis matrix B described above and concatenate the selectedcolumns K_(c) to form a common basis matrix B_(c). In certainembodiments, the common basis matrix B_(c) may be chosen per one or moreof polarization and layer.

To further illustrate this step, consider the case when the first basis(described above) contains K basis vectors. A selection of K_(c)<K outof the K vectors may be performed. In certain embodiments, these K_(c)selected basis vectors then form a second basis (which may be referredto herein as the common basis or the second set of candidatefrequency-domain components). Using a matrix representation, the subsetselection can be seen as selecting K_(c)<K columns of the first basismatrix B and concatenating these columns to form the common basis matrixB_(c). For instance, the selection can be represented as a functionI_(c)(m) being a mapping from an integer m to an integer value I_(c)(m),such that I_(c)(m) is defined for 0≤m≤K_(c)−1 and 0≤I_(c)(m)≤K−1 whereit may also be so that I_(c)(m₁)≠I_(c)(m₂) when m₁≠m₂. This selectionfunction may then be used to describe the common basis as:B _(c)=[B(I _(c)(0))B(I _(c)(1)) . . . B(I _(c)(K _(c)−1))],where B(m) denotes the m:th column of the matrix B. Note that B_(c) willspan a subset of space spanned by B.

Note further that there will be in total

$\quad\begin{pmatrix}K \\{Kc}\end{pmatrix}$possible selections (where

$\left. {{\begin{pmatrix}A \\B\end{pmatrix} =}\frac{A!}{{B!}{\left( {A - B} \right)!}}} \right)$and hence also selection functions I_(c)(m). One of these selections canbe represented using log

${\left\lceil {\log\; 2\left( \begin{pmatrix}K \\{Kc}\end{pmatrix} \right)} \right\rceil\mspace{14mu}{bits}},$bits for instance using a combinatorial number system. In certainembodiments, wireless device 510 may perform this selection, representit using a number of bits and then signal this information to networknode 560 (e.g., a gNB), for example as part of the CSI report.

In certain embodiments, the common basis B_(c) represents the channeland as such it may be used for both polarizations and all layers in theprecoder. In certain embodiments, however, B_(c) may instead be chosenper polarization and/or layer.

The present disclosure contemplates that Kc may be determined in anysuitable manner. As one example, Kc may be specified in the standard. Asanother example, Kc may be configurable. As still another example, Kcmay be rank dependent and may be thus be expressed as Kc(r).

In the fourth step, wireless device 510 determines, for eachspatial-domain component of the set of spatial-domain components, aspatial-domain component-specific set of frequency-domain components asa subset of the second set of candidate frequency-domain components. Incertain embodiments, each frequency-domain component in thespatial-domain component-specific set of frequency-domain components maybe associated with a non-zero coefficient of the set of linearcombination coefficients. In certain embodiments, wireless device 510may determine if the associated one or more linear combiningcoefficients are non-zero.

In determining the spatial-domain component-specific set offrequency-domain components, wireless device 510 may perform abeam-specific selection of the columns from the common basis. Forexample, a beam-specific basis selection may be made by wireless device510 from the second set of candidate frequency-domain components, whichmay in certain embodiments be realized as a selection of columns fromthe common basis B_(c) described above.

In some cases, it may be so that beam i selects K_(b)(i) out of theK_(c) basis vectors from the common basis, where Kb(i)≤Kc, and theseK_(b)(i) vectors will then represent a beam-specific basis for beam i=0,. . . , 2L−1.

If, for instance, the beam-specific selection is represented as afunction I_(b)(i,m) being a mapping from an integer m to an integervalue I_(b)(i,m), such that I_(b)(i,m) is defined for 0≤m≤K_(b)(i)−1 and1≤I_(b)(i,m)≤K_(c), where it may also be so that I_(b)(i,m₁)≠I_(b)(i,m₂)when m₁≠m₂. The selection function could be used to describe the beamspecific basis as:B _(i)=[B _(c)(I _(b)(i,0))B _(c)(I _(b)(i,1)) . . . B _(c)(I_(b)(i,Kb(i)−1))].

Note that there will be in total

$\quad\begin{pmatrix}K \\{K_{b}(i)}\end{pmatrix}$possible selections and hence also selection functions I_(b)(i,m)meaning that it can be represented using

$\left\lceil {\log\; 2\left( \begin{pmatrix}{Kc} \\{{Kb}(i)}\end{pmatrix} \right)} \right\rceil$bits. In certain embodiments, wireless device 510 may perform thisselection, represent it using a number of bits, and then signal thisinformation to network node 560 (e.g., a gNB), for example as part ofthe CSI report.

In certain embodiments, B_(i)=B_(i+1), implying that the differentpolarizations of the precoder share the same frequency-domain basisselection. Hence, there may be only one beam-specific frequency-domainbasis used by beams corresponding to different polarizations.

In certain embodiments, wireless device 510 may derive c_(l,i) for eachbeam such that c_(l,i) is a linear combination of the K_(b)(i)frequency-domain basis vectors selected as described above. Hence, it isassumed that c_(l,i)=B_(i)a_(l,i) where a_(l,i) is a K_(b)(i)×1 vectorof complex values.

In certain embodiments, wireless device 510 may derive a complex valuedvector a_(l,i) and also create a quantized version of it denoted ã(l,i).This quantized vector ã(l,i) can be represented with a finite set ofbits that could be signaled by wireless device 510 to network node 560(e.g., a gNB), for example as part of the CS report.

As described above, in certain embodiments wireless device 510 maydetermine if the associated one or more linear combining coefficientsare non-zero. For example, in certain embodiments wireless device 510may determine linear combining coefficients for each combination offrequency-domain components of the second set of candidatefrequency-domain components and spatial-domain components. Wirelessdevice 510 may inspect the amplitude of the determined linear combiningcoefficients, quantize the amplitude of the coefficients, and determinethat amplitudes that are below a threshold are regarded as zerocoefficients. In certain embodiments, wireless device 510 will onlyinclude the frequency-domain components corresponding to non-zerocoefficients in the spatial-domain component-specific set offrequency-domain components.

In certain embodiments, wireless device 510 may be configured toconsider some coefficients as zero even if the quantized amplitude isnot zero. This may be due to a limit imposed on how many non-zerocoefficients, K_(nz), that wireless device 510 can report. In such acase, wireless device 510 may sort the coefficients according toamplitude and set the 2LK_(c)−K_(nz) weakest coefficients as zerocoefficients.

In a fifth step, wireless device 510 then transmits, to network node560, the CSI report. In certain embodiments, the CSI report may comprisean indication of: the determined second set of candidatefrequency-domain components; the determined spatial-domaincomponent-specific sets of frequency-domain components; and the non-zerocoefficients of the set of linear combination coefficients.

Although the description of the example embodiment above describesfirst, second, third, fourth, and fifth steps, this is for ease ofexplanation only and is not intended to limit the scope of the presentdisclosure to the precise order of steps described herein. Rather, thepresent disclosure contemplates that the steps of the example embodimentdescribed above may be performed in any suitable order. For instance, insome embodiments the wireless device may perform the steps jointly or ina different order.

Although the description of the example embodiment above described aseparate encoding of the information obtained by I_(c)(m), I_(b)(i,m)and a_(l,i) in some cases it may be beneficial to instead conduct ajoint encoding of these entities.

Thus, in certain embodiments the determined beam-specific basisselections I_(b)(i,m), 0≤m≤K_(b)(i)−1 for all the beams i=0, . . . ,2L−1 may be jointly encoded into a single parameter, mapped to a numberof bits, and fed back as part of the CSI report.

In certain embodiments, the determined beam-specific basis selectionsI_(b)(i,m), 0≤m≤K_(b)(i)−1 as well as an indication of K_(b)(i) may bejointly encoded into a single parameter, mapped to a number of bits, andfed back as part of the CSI report.

In certain embodiments, the determined beam-specific basis selectionsmay be jointly encoded with an indication of which, if any, linearcombining coefficients a_(l,i,m) are non-zero.

According to another example embodiment, a network node, such networknode 560 (e.g., a gNB), may perform a method for receiving a CSI reportfor a DL channel. The CSI report may indicate a plurality of precodervectors. Each of the precoder vectors may correspond to a frequencysub-band of the bandwidth of the downlink channel. In certainembodiments, a size of the frequency sub-band may be an integer numberof PRBs. A precoder vector may be expressed as a linear combination ofspatial-domain components and frequency-domain components. The pluralityof precoder vectors may be indicated by indicating the frequency-domaincomponents and a set of linear combination coefficients.

According to this example embodiment, network node 560 receives, from awireless device, such as wireless device 510 (e.g., a UE), the CSIreport. The CSI report may comprise an indication of: a second set ofcandidate frequency-domain components being a subset of a first set ofcandidate frequency-domain components; one or more spatial-domaincomponent-specific sets of frequency-domain components being subsets ofthe second set of candidate frequency-domain components, eachfrequency-domain component in the one or more spatial-domaincomponent-specific sets of frequency-domain components being associatedwith non-zero coefficients of the set of linear combinationcoefficients; and the non-zero coefficients.

Network node 560 determines one or more precoder vectors based upon theindication received in the CSI report.

In certain embodiments, network node 560 may use one of the determinedone or more precoder vectors to perform a transmission to wirelessdevice 510.

In certain embodiments, network node 560 may use a different precodervector from the one or more determined precoder vectors to perform atransmission to wireless device 510.

In certain embodiments, network node 560 may perform the following steps(or a subset thereof) to determine the one or more precoder vectorsbased upon the indication received in the CSI report. Network node 560may determine, from the spatial-domain component-specific subset offrequency-domain components, one or more spatial-domain components. Eachcomponent in the spatial-domain component-specific subset offrequency-domain components may be associated with one or more linearcombining coefficients. Network node 560 may determine a first set ofcandidate frequency-domain components. The first set of candidatefrequency-domain components may include the second set of candidatefrequency-domain components. Network node 560 may determine a set ofspatial-domain components.

In certain embodiments, the candidate frequency-domain components may beorthogonal basis vectors. In certain embodiments, the orthogonal basisvectors may be discrete Fourier transform vectors.

In certain embodiments, a size of the frequency sub-band may be one PRB.In certain embodiments, a size of the frequency sub-band may be aninteger number of PRBs.

FIG. 6 is a flowchart illustrating an example of a method 600 performedby a wireless device, in accordance with certain embodiments. Moreparticularly, FIG. 6 illustrates a method 600 performed by a wirelessdevice for transmitting a CSI report for a DL channel. The CSI reportindicates a plurality of precoder vectors. Each of the precoder vectorscorresponds to a frequency sub-band of the bandwidth of the DL channel.A precoder vector is expressed as a linear combination of spatial-domaincomponents and frequency-domain components. Indicating the plurality ofprecoder vectors comprises indicating the frequency-domain componentsand a set of linear combination coefficients.

Method 600 begins at step 601, where the wireless device obtains a firstset of candidate frequency-domain components. In certain embodiments,the candidate frequency-domain components may be orthogonal basisvectors. In certain embodiments, the orthogonal basis vectors may bediscrete Fourier transform vectors. In certain embodiments, a size ofthe frequency sub-band may be an integer number of PRBs.

In certain embodiments, obtaining the first set of candidatefrequency-domain components may comprise defining a first basisconstituting a number of basis vectors.

In certain embodiments, obtaining the first set of candidatefrequency-domain components may comprise one of: obtaining the first setof candidate frequency-domain components by accessing a predefinedtable; obtaining the first set of candidate frequency-domain componentsvia higher layer signaling; and determining the first set of candidatefrequency-domain components.

At step 602, the wireless device determines a set of spatial-domaincomponents.

At step 603, the wireless device determines a second set of candidatefrequency-domain components as a subset of the first set of candidatefrequency-domain components. In certain embodiments, determining thesecond set of candidate frequency-domain components as a subset of thefirst set of candidate frequency-domain components may comprise:analyzing an estimate of the DL channel to determine one or moreproperties of the DL channel; and selecting the second set of candidatefrequency-domain components from the first set of candidatefrequency-domain components based on the determined one or moreproperties of the DL channel.

In certain embodiments, determining the second set of candidatefrequency-domain components as a subset of the first set of candidatefrequency-domain components may comprise creating a common basis for allspatial-domain components.

At step 604, the wireless device determines, for each spatial-domaincomponent of the set of spatial-domain components, a spatial-domaincomponent-specific set of frequency-domain components as a subset of thesecond set of candidate frequency-domain components, wherein eachfrequency-domain component in the spatial-domain component-specific setof frequency-domain components is associated with a non-zero coefficientof the set of linear combination coefficients. In certain embodiments,determining the spatial-domain component-specific set offrequency-domain components may comprise determining if the associatedone or more linear combining coefficients are non-zero.

In certain embodiments, the first set of candidate frequency-domaincomponents may be a first basis matrix B comprising K basis vectors. Incertain embodiments, determining the second set of candidatefrequency-domain components as the subset of the first set of candidatefrequency-domain components may comprise selecting K_(c)<K columns ofthe first basis matrix B and concatenating the selected columns K_(c) toform a common basis matrix B_(c). In certain embodiments, the commonbasis matrix B_(c) may be chosen per one or more of polarization andlayer. In certain embodiments, determining the spatial-domaincomponent-specific frequency-domain components may comprise selecting aselection of columns from the common basis matrix B_(c).

At step 605, the wireless device transmits, to a network node, the CSIreport comprising an indication of: the determined second set ofcandidate frequency-domain components, the determined spatial-domaincomponent-specific sets of frequency-domain components; and the non-zerocoefficients of the set of linear combination coefficients.

FIG. 7 is a block diagram illustrating an example of a virtualapparatus, in accordance with certain embodiments. More particularly,FIG. 7 illustrates a schematic block diagram of an apparatus 700 in awireless network (for example, the wireless network shown in FIG. 5).The apparatus may be implemented in a wireless device (e.g., wirelessdevice 510 shown in FIG. 5). Apparatus 700 is operable to carry out theexample method described with reference to FIG. 6 and possibly any otherprocesses or methods disclosed herein. It is also to be understood thatthe method of FIG. 6 is not necessarily carried out solely by apparatus700. At least some operations of the method can be performed by one ormore other entities.

Virtual Apparatus 700 may comprise processing circuitry, which mayinclude one or more microprocessor or microcontrollers, as well as otherdigital hardware, which may include digital signal processors (DSPs),special-purpose digital logic, and the like. The processing circuitrymay be configured to execute program code stored in memory, which mayinclude one or several types of memory such as read-only memory (ROM),random-access memory, cache memory, flash memory devices, opticalstorage devices, etc. Program code stored in memory includes programinstructions for executing one or more telecommunications and/or datacommunications protocols as well as instructions for carrying out one ormore of the techniques described herein, in several embodiments. In someimplementations, the processing circuitry may be used to cause receivingunit 702, determining unit 704, communication unit 706, and any othersuitable units of apparatus 700 to perform corresponding functionsaccording one or more embodiments of the present disclosure.

In certain embodiments, apparatus 700 may be a UE. In certainembodiments, apparatus 700 may be configured to perform a method fortransmitting a CSI report for a DL channel. The CSI report may indicatea plurality of precoder vectors. Each of the precoder vectors maycorrespond to a frequency sub-band of the bandwidth of the DL channel.In certain embodiments, a size of the frequency sub-band is an integernumber of PRBs. A precoder vector may be expressed as a linearcombination of spatial-domain components and frequency-domain componentsIndicating the plurality of precoder vectors may comprise indicating thefrequency-domain components and a set of linear combinationcoefficients.

As illustrated in FIG. 7, apparatus 700 includes receiving unit 702,determining unit 704, and communication unit 706. Receiving unit 702 maybe configured to perform the receiving functions of apparatus 700. Forexample, receiving unit 702 may be configured to receive a channel. Asanother example, receiving unit 702 may be configured to obtain a firstset of candidate frequency-domain components. In certain embodiments,receiving unit 702 may be configured to receive the first set ofcandidate frequency-domain components (e.g., via higher layersignalling).

Receiving unit 702 may receive any suitable information (e.g., fromanother wireless device or a network node). Receiving unit 702 mayinclude a receiver and/or a transceiver, such as RF transceivercircuitry 522 described above in relation to FIG. 5. Receiving unit 702may include circuitry configured to receive messages and/or signals(wireless or wired). In particular embodiments, receiving unit 702 maycommunicate received messages and/or signals to determining unit 704and/or any other suitable unit of apparatus 700. The functions ofreceiving unit 702 may, in certain embodiments, be performed in one ormore distinct units.

Determining unit 704 may perform the processing functions of apparatus700. For example, determining unit 704 may be configured to obtain afirst set of candidate frequency-domain components. In certainembodiments, determining unit 704 may be configured to define a firstbasis constituting a number of basis vectors. In certain embodiments,determining unit 704 may be configured to obtain the first set ofcandidate frequency-domain components by accessing a predefined table.In certain embodiments, determining unit 704 may be configured to obtainthe first set of candidate frequency-domain components by determiningthe first set of candidate frequency-domain components. In certainembodiments, determining unit 704 may be configured to obtain the firstset of candidate frequency-domain components via higher layersignalling.

In certain embodiments, the candidate frequency-domain components may beorthogonal basis vectors. In certain embodiments, the orthogonal basisvectors may be discrete Fourier transform vectors.

As another example, determining unit 704 may be configured to determinea set of spatial-domain components.

As still another example, determining unit 704 may be configured todetermine a second set of candidate frequency-domain components as asubset of the first set of candidate frequency-domain components. Incertain embodiments, determining unit 704 may be configured to estimatea DL channel. In certain embodiments, determining unit 704 may beconfigured to analyze an estimate of the DL channel to determine one ormore properties of the DL channel and to select the second set ofcandidate frequency-domain components from the first set of candidatefrequency-domain components based on the determined one or moreproperties of the DL channel.

In certain embodiments, determining unit 704 may be configured to createa common basis for all spatial-domain components. In certainembodiments, the first set of candidate frequency-domain components maybe a first basis matrix B comprising K basis vectors. Determining unit704 may be configured to select K_(c)<K columns of the first basismatrix B. Determining unit 704 may be configured to concatenate theselected columns K, to form a common basis matrix B_(c). In certainembodiments, the common basis matrix B_(c) may be chosen per one or moreof polarization and layer.

As yet another example, determining unit 704 may be configured todetermine, for each spatial-domain component of the set ofspatial-domain components, a spatial-domain component-specific set offrequency-domain components as a subset of the second set of candidatefrequency-domain components, wherein each frequency-domain component inthe spatial-domain component-specific set of frequency-domain componentsis associated with a non-zero coefficient of the set of linearcombination coefficients. In certain embodiments, determining unit 704may be configured to determine if the associated one or more linearcombining coefficients are non-zero. In certain embodiments, determiningunit 704 may be configured to select a selection of columns from thecommon basis matrix B_(c).

As another example, determining unit 704 may be configured to generate aCSI report. The CSI report may comprise an indication of the determinedsecond set of candidate frequency-domain components; the determinedspatial-domain component-specific sets of frequency-domain components;and the non-zero coefficients of the set of linear combinationcoefficients.

As another example, determining unit 704 may be configured to provideuser data.

Determining unit 704 may include or be included in one or moreprocessors, such as processing circuitry 520 described above in relationto FIG. 5. Determining unit 704 may include analog and/or digitalcircuitry configured to perform any of the functions of determining unit704 and/or processing circuitry 520 described above. The functions ofdetermining unit 704 may, in certain embodiments, be performed in one ormore distinct units.

Communication unit 706 may be configured to perform the transmissionfunctions of apparatus 700. For example, communication unit 706 may beconfigured to transmit, to a network node, the CSI report comprising anindication of: the determined second set of candidate frequency-domaincomponents; the determined spatial-domain component-specific sets offrequency-domain components; and the non-zero coefficients of the set oflinear combination coefficients. As another example, communication unit706 may be configured to forward user data to a host computer via atransmission to a network node.

Communication unit 706 may transmit messages (e.g., to another wirelessdevice and/or a network node). Communication unit 706 may include atransmitter and/or a transceiver, such as RF transceiver circuitry 522described above in relation to FIG. 5. Communication unit 706 mayinclude circuitry configured to transmit messages and/or signals (e.g.,through wireless or wired means). In particular embodiments,communication unit 706 may receive messages and/or signals fortransmission from determining unit 704 or any other unit of apparatus700. The functions of communication unit 704 may, in certainembodiments, be performed in one or more distinct units.

FIG. 8 is a flowchart illustrating an example of a method 800 performedby a network node, in accordance with certain embodiments. Moreparticularly, FIG. 8 illustrates a method 800 performed by a networknode for receiving a CSI report for a DL channel. The CSI reportindicates a plurality of precoder vectors. Each of the precoder vectorscorresponds to a frequency sub-band of the bandwidth of the DL channel.A precoder vector is expressed as a linear combination of spatial-domaincomponents and frequency-domain components. Indicating the plurality ofprecoder vectors comprises indicating the frequency-domain componentsand a set of linear combination coefficients.

Method 800 begins at step 801, where the network node receives, from awireless device, the CSI report comprising an indication of: a secondset of candidate frequency-domain components being a subset of a firstset of candidate frequency-domain components; one or more spatial-domaincomponent-specific sets of frequency-domain components being subsets ofthe second set of candidate frequency-domain components, eachfrequency-domain component in the one or more spatial-domaincomponent-specific sets of frequency-domain components being associatedwith non-zero coefficients of the set of linear combinationcoefficients; and the non-zero coefficients.

In certain embodiments, a size of the frequency sub-band may be aninteger number of PRBs.

At step 802, the network node determines one or more precoder vectorsbased upon the indication received in the CSI report.

In certain embodiments, the method may further comprise using one of thedetermined one or more precoder vectors to perform a transmission to thewireless device.

In certain embodiments, the method may further comprise using adifferent precoder vector from the one or more determined precodervectors to perform a transmission to the wireless device.

FIG. 9 is a block diagram illustrating an example of a virtualapparatus, in accordance with certain embodiments. More particularly,FIG. 9 illustrates a schematic block diagram of an apparatus 900 in awireless network (for example, the wireless network shown in FIG. 5).The apparatus may be implemented in a network node (e.g., network node560 shown in FIG. 5). Apparatus 900 is operable to carry out the examplemethod described with reference to FIG. 8 and possibly any otherprocesses or methods disclosed herein. It is also to be understood thatthe method of FIG. 8 is not necessarily carried out solely by apparatus900. At least some operations of the method can be performed by one ormore other entities.

Virtual Apparatus 900 may comprise processing circuitry, which mayinclude one or more microprocessor or microcontrollers, as well as otherdigital hardware, which may include digital signal processors (DSPs),special-purpose digital logic, and the like. The processing circuitrymay be configured to execute program code stored in memory, which mayinclude one or several types of memory such as read-only memory (ROM),random-access memory, cache memory, flash memory devices, opticalstorage devices, etc. Program code stored in memory includes programinstructions for executing one or more telecommunications and/or datacommunications protocols as well as instructions for carrying out one ormore of the techniques described herein, in several embodiments. In someimplementations, the processing circuitry may be used to cause receivingunit 902, determining unit 904, communication unit 906, and any othersuitable units of apparatus 900 to perform corresponding functionsaccording one or more embodiments of the present disclosure.

In certain embodiments, apparatus 900 may be an eNB or a gNB. Apparatus900 may be configured to perform a method for receiving a CSI report fora DL channel. The CSI report may indicate a plurality of precodervectors. Each of the precoder vectors may correspond to a frequencysub-band of the bandwidth of the DL channel. In certain embodiments, asize of the frequency sub-band may be an integer number of PRBs. Aprecoder vector may be expressed as a linear combination ofspatial-domain components and frequency-domain components. Indicatingthe plurality of precoder vectors may comprise indicating thefrequency-domain components and a set of linear combinationcoefficients.

As illustrated in FIG. 9, apparatus 900 includes receiving unit 902,determining unit 904, and communication unit 906. Receiving unit 902 maybe configured to perform the receiving functions of apparatus 900. Forexample, receiving unit 902 may be configured to receive, from awireless device, the CSI report comprising an indication of: a secondset of candidate frequency-domain components being a subset of a firstset of candidate frequency-domain components; one or more spatial-domaincomponent-specific sets of frequency-domain components being subsets ofthe second set of candidate frequency-domain components, eachfrequency-domain component in the one or more spatial-domaincomponent-specific sets of frequency-domain components being associatedwith non-zero coefficients of the set of linear combinationcoefficients; and the non-zero coefficients. As another example,receiving unit 902 may be configured to obtain user data.

Receiving unit 902 may receive any suitable information (e.g., from awireless device or another network node). Receiving unit 902 may includea receiver and/or a transceiver, such as RF transceiver circuitry 572described above in relation to FIG. 5. Receiving unit 902 may includecircuitry configured to receive messages and/or signals (wireless orwired). In particular embodiments, receiving unit 902 may communicatereceived messages and/or signals to determining unit 904 and/or anyother suitable unit of apparatus 900. The functions of receiving unit902 may, in certain embodiments, be performed in one or more distinctunits.

Determining unit 904 may perform the processing functions of apparatus900. For example, determining unit 904 may be configured to determineone or more precoder vectors based upon the indication received in theCSI report.

In certain embodiments, determining unit 904 may be configured todetermine, from the spatial-domain component-specific subset offrequency-domain components, one or more spatial-domain components,wherein each component in the spatial-domain component-specific subsetof frequency-domain components is associated with one or more linearcombining coefficients. In certain embodiments, determining unit 904 maybe configured to determine a first set of candidate frequency-domaincomponents, the first set of candidate frequency-domain componentscomprising the second set of candidate frequency-domain components. Incertain embodiments, determining unit 904 may be configured to determinea set of spatial-domain components.

As another example, determining unit 904 may be configured to use one ofthe determined one or more precoder vectors to perform a transmission tothe wireless device. As another example, determining unit 904 may beconfigured to use a different precoder vector from the one or moredetermined precoder vectors to perform a transmission to the wirelessdevice.

As another example, determining unit 904 may be configured to obtainuser data.

Determining unit 904 may include or be included in one or moreprocessors, such as processing circuitry 570 described above in relationto FIG. 5. Determining unit 904 may include analog and/or digitalcircuitry configured to perform any of the functions of determining unit904 and/or processing circuitry 170 described above. The functions ofdetermining unit 904 may, in certain embodiments, be performed in one ormore distinct units.

Communication unit 906 may be configured to perform the transmissionfunctions of apparatus 900. For example, communication unit 906 may beconfigured to use one of the determined one or more precoder vectors toperform a transmission to the wireless device. As another example,communication unit 906 may be configured to use a different precodervector from the one or more determined precoder vectors to perform atransmission to the wireless device. As another example, communicationunit 906 may be configured to forward the user data to a host computeror a wireless device.

Communication unit 906 may transmit messages (e.g., to a wireless deviceand/or another network node) Communication unit 906 may include atransmitter and/or a transceiver, such as RF transceiver circuitry 572described above in relation to FIG. 5. Communication unit 906 mayinclude circuitry configured to transmit messages and/or signals (e.g.,through wireless or wired means). In particular embodiments,communication unit 906 may receive messages and/or signals fortransmission from determining unit 904 or any other unit of apparatus900. The functions of communication unit 904 may, in certainembodiments, be performed in one or more distinct units.

The term unit may have conventional meaning in the field of electronics,electrical devices and/or electronic devices and may include, forexample, electrical and/or electronic circuitry, devices, modules,processors, memories, logic solid state and/or discrete devices,computer programs or instructions for carrying out respective tasks,procedures, computations, outputs, and/or displaying functions, and soon, as such as those that are described herein.

In some embodiments a computer program, computer program product orcomputer readable storage medium comprises instructions which whenexecuted on a computer perform any of the embodiments disclosed herein.In further examples the instructions are carried on a signal or carrierand which are executable on a computer wherein when executed perform anyof the embodiments disclosed herein.

FIG. 10 illustrates an example user equipment, in accordance withcertain embodiments. As used herein, a user equipment or UE may notnecessarily have a user in the sense of a human user who owns and/oroperates the relevant device. Instead, a UE may represent a device thatis intended for sale to, or operation by, a human user but which maynot, or which may not initially, be associated with a specific humanuser (e.g., a smart sprinkler controller). Alternatively, a UE mayrepresent a device that is not intended for sale to, or operation by, anend user but which may be associated with or operated for the benefit ofa user (e.g., a smart power meter). UE 1000 may be any UE identified bythe 3^(rd) Generation Partnership Project (3GPP), including a NB-IoT UE,a machine type communication (MTC) UE, and/or an enhanced MTC (eMTC) UE.UE 1000, as illustrated in FIG. 10, is one example of a wireless deviceconfigured for communication in accordance with one or morecommunication standards promulgated by the 3^(rd) Generation PartnershipProject (3GPP), such as 3GPP's GSM, UMTS, LTE, and/or 5G standards. Asmentioned previously, the term wireless device and UE may be usedinterchangeable. Accordingly, although FIG. 10 is a UE, the componentsdiscussed herein are equally applicable to a wireless device, andvice-versa.

In FIG. 10, UE 1000 includes processing circuitry 1001 that isoperatively coupled to input/output interface 1005, radio frequency (RF)interface 1009, network connection interface 1011, memory 1015 includingrandom access memory (RAM) 1017, read-only memory (ROM) 1019, andstorage medium 1021 or the like, communication subsystem 1031, powersource 1033, and/or any other component, or any combination thereof.Storage medium 1021 includes operating system 1023, application program1025, and data 1027. In other embodiments, storage medium 1021 mayinclude other similar types of information. Certain UEs may utilize allof the components shown in FIG. 10, or only a subset of the components.The level of integration between the components may vary from one UE toanother UE Further, certain UEs may contain multiple instances of acomponent, such as multiple processors, memories, transceivers,transmitters, receivers, etc.

In FIG. 10, processing circuitry 1001 may be configured to processcomputer instructions and data. Processing circuitry 1001 may beconfigured to implement any sequential state machine operative toexecute machine instructions stored as machine-readable computerprograms in the memory, such as one or more hardware-implemented statemachines (e.g., in discrete logic, FPGA, ASIC, etc.); programmable logictogether with appropriate firmware; one or more stored program,general-purpose processors, such as a microprocessor or Digital SignalProcessor (DSP), together with appropriate software; or any combinationof the above. For example, the processing circuitry 1001 may include twocentral processing units (CPUs). Data may be information in a formsuitable for use by a computer.

In the depicted embodiment, input/output interface 1005 may beconfigured to provide a communication interface to an input device,output device, or input and output device. UE 1000 may be configured touse an output device via input/output interface 1005. An output devicemay use the same type of interface port as an input device. For example,a USB port may be used to provide input to and output from UE 1000. Theoutput device may be a speaker, a sound card, a video card, a display, amonitor, a printer, an actuator, an emitter, a smartcard, another outputdevice, or any combination thereof. UE 1000 may be configured to use aninput device via input/output interface 1005 to allow a user to captureinformation into UE 1000. The input device may include a touch-sensitiveor presence-sensitive display, a camera (e.g., a digital camera, adigital video camera, a web camera, etc.), a microphone, a sensor, amouse, a trackball, a directional pad, a trackpad, a scroll wheel, asmartcard, and the like. The presence-sensitive display may include acapacitive or resistive touch sensor to sense input from a user. Asensor may be, for instance, an accelerometer, a gyroscope, a tiltsensor, a force sensor, a magnetometer, an optical sensor, a proximitysensor, another like sensor, or any combination thereof. For example,the input device may be an accelerometer, a magnetometer, a digitalcamera, a microphone, and an optical sensor.

In FIG. 10, RF interface 1009 may be configured to provide acommunication interface to RF components such as a transmitter, areceiver, and an antenna. Network connection interface 1011 may beconfigured to provide a communication interface to network 1043 a.Network 1043 a may encompass wired and/or wireless networks such as alocal-area network (LAN), a wide-area network (WAN), a computer network,a wireless network, a telecommunications network, another like networkor any combination thereof. For example, network 1043 a may comprise aWi-Fi network. Network connection interface 1011 may be configured toinclude a receiver and a transmitter interface used to communicate withone or more other devices over a communication network according to oneor more communication protocols, such as Ethernet, TCP/IP, SONET, ATM,or the like Network connection interface 1011 may implement receiver andtransmitter functionality appropriate to the communication network links(e.g., optical, electrical, and the like). The transmitter and receiverfunctions may share circuit components, software or firmware, oralternatively may be implemented separately.

RAM 1017 may be configured to interface via bus 1002 to processingcircuitry 1001 to provide storage or caching of data or computerinstructions during the execution of software programs such as theoperating system, application programs, and device drivers. ROM 1019 maybe configured to provide computer instructions or data to processingcircuitry 1001. For example, ROM 1019 may be configured to storeinvariant low-level system code or data for basic system functions suchas basic input and output (I/O), startup, or reception of keystrokesfrom a keyboard that are stored in a non-volatile memory. Storage medium1021 may be configured to include memory such as RAM, ROM, programmableread-only memory (PROM), erasable programmable read-only memory (EPROM),electrically erasable programmable read-only memory (EEPROM), magneticdisks, optical disks, floppy disks, hard disks, removable cartridges, orflash drives. In one example, storage medium 1021 may be configured toinclude operating system 1023, application program 1025 such as a webbrowser application, a widget or gadget engine or another application,and data file 1027. Storage medium 1021 may store, for use by UE 1000,any of a variety of various operating systems or combinations ofoperating systems.

Storage medium 1021 may be configured to include a number of physicaldrive units, such as redundant array of independent disks (RAID), floppydisk drive, flash memory, USB flash drive, external hard disk drive,thumb drive, pen drive, key drive, high-density digital versatile disc(HD-DVD) optical disc drive, internal hard disk drive, Blu-Ray opticaldisc drive, holographic digital data storage (HDDS) optical disc drive,external mini-dual in-line memory module (DIMM), synchronous dynamicrandom access memory (SDRAM), external micro-DIMM SDRAM, smartcardmemory such as a subscriber identity module or a removable user identity(SIM/RUIM) module, other memory, or any combination thereof. Storagemedium 1021 may allow UE 1000 to access computer-executableinstructions, application programs or the like, stored on transitory ornon-transitory memory media, to off-load data, or to upload data. Anarticle of manufacture, such as one utilizing a communication system maybe tangibly embodied in storage medium 1021, which may comprise a devicereadable medium.

In FIG. 10, processing circuitry 1001 may be configured to communicatewith network 1043 b using communication subsystem 1031. Network 1043 aand network 1043 b may be the same network or networks or differentnetwork or networks. Communication subsystem 1031 may be configured toinclude one or more transceivers used to communicate with network 1043b. For example, communication subsystem 1031 may be configured toinclude one or more transceivers used to communicate with one or moreremote transceivers of another device capable of wireless communicationsuch as another wireless device, LE, or base station of a radio accessnetwork (RAN) according to one or more communication protocols, such asIEEE 802.11, CDMA, WCDMA, GSM, LTE, UTRAN, WiMax, or the like. Eachtransceiver may include transmitter 1033 and/or receiver 1035 toimplement transmitter or receiver functionality, respectively,appropriate to the RAN links (e.g., frequency allocations and the like).Further, transmitter 1033 and receiver 1035 of each transceiver mayshare circuit components, software or firmware, or alternatively may beimplemented separately.

In the illustrated embodiment, the communication functions ofcommunication subsystem 1031 may include data communication, voicecommunication, multimedia communication, short-range communications suchas Bluetooth, near-field communication, location-based communicationsuch as the use of the global positioning system (GPS) to determine alocation, another like communication function, or any combinationthereof. For example, communication subsystem 1031 may include cellularcommunication, Wi-Fi communication, Bluetooth communication, and GPScommunication. Network 1043 b may encompass wired and/or wirelessnetworks such as a local-area network (LAN), a wide-area network (WAN),a computer network, a wireless network, a telecommunications network,another like network or any combination thereof. For example, network1043 b may be a cellular network, a Wi-Fi network, and/or a near-fieldnetwork. Power source 1013 may be configured to provide alternatingcurrent (AC) or direct current (DC) power to components of UE 1000.

The features, benefits and/or functions described herein may beimplemented in one of the components of UE 1000 or partitioned acrossmultiple components of UE 1000. Further, the features, benefits, and/orfunctions described herein may be implemented in any combination ofhardware, software or firmware. In one example, communication subsystem1031 may be configured to include any of the components describedherein. Further, processing circuitry 1001 may be configured tocommunicate with any of such components over bus 1002. In anotherexample, any of such components may be represented by programinstructions stored in memory that when executed by processing circuitry1001 perform the corresponding functions described herein. In anotherexample, the functionality of any of such components may be partitionedbetween processing circuitry 1001 and communication subsystem 1031. Inanother example, the non-computationally intensive functions of any ofsuch components may be implemented in software or firmware and thecomputationally intensive functions may be implemented in hardware.

FIG. 11 illustrates an example virtualization environment in accordancewith some embodiments. More particularly, FIG. 11 is a schematic blockdiagram illustrating a virtualization environment 1100 in whichfunctions implemented by some embodiments may be virtualized. In thepresent context, virtualizing means creating virtual versions ofapparatuses or devices which may include virtualizing hardwareplatforms, storage devices and networking resources. As used herein,virtualization can be applied to a node (e.g., a virtualized basestation or a virtualized radio access node) or to a device (e.g., a UE,a wireless device or any other type of communication device) orcomponents thereof and relates to an implementation in which at least aportion of the functionality is implemented as one or more virtualcomponents (e.g., via one or more applications, components, functions,virtual machines or containers executing on one or more physicalprocessing nodes in one or more networks).

In some embodiments, some or all of the functions described herein maybe implemented as virtual components executed by one or more virtualmachines implemented in one or more virtual environments 1100 hosted byone or more of hardware nodes 1130. Further, in embodiments in which thevirtual node is not a radio access node or does not require radioconnectivity (e.g., a core network node), then the network node may beentirely virtualized.

The functions may be implemented by one or more applications 1120 (whichmay alternatively be called software instances, virtual appliances,network functions, virtual nodes, virtual network functions, etc.)operative to implement some of the features, functions, and/or benefitsof some of the embodiments disclosed herein. Applications 1120 are runin virtualization environment 1100 which provides hardware 1130comprising processing circuitry 1160 and memory 1190. Memory 1190contains instructions 1195 executable by processing circuitry 1160whereby application 1120 is operative to provide one or more of thefeatures, benefits, and/or functions disclosed herein.

Virtualization environment 1100, comprises general-purpose orspecial-purpose network hardware devices 1130 comprising a set of one ormore processors or processing circuitry 1160, which may be commercialoff-the-shelf (COTS) processors, dedicated Application SpecificIntegrated Circuits (ASICs), or any other type of processing circuitryincluding digital or analog hardware components or special purposeprocessors. Each hardware device may comprise memory 1190-1 which may benon-persistent memory for temporarily storing instructions 1195 orsoftware executed by processing circuitry 1160. Each hardware device maycomprise one or more network interface controllers (NICs) 1170, alsoknown as network interface cards, which include physical networkinterface 1180. Each hardware device may also include non-transitory,persistent, machine-readable storage media 1190-2 having stored thereinsoftware 1195 and/or instructions executable by processing circuitry1160. Software 1195 may include any type of software including softwarefor instantiating one or more virtualization layers 1150 (also referredto as hypervisors), software to execute virtual machines 1140 as well assoftware allowing it to execute functions, features and/or benefitsdescribed in relation with some embodiments described herein.

Virtual machines 1140, comprise virtual processing, virtual memory,virtual networking or interface and virtual storage, and may be run by acorresponding virtualization layer 1150 or hypervisor. Differentembodiments of the instance of virtual appliance 1120 may be implementedon one or more of virtual machines 1140, and the implementations may bemade in different ways.

During operation, processing circuitry 1160 executes software 1195 toinstantiate the hypervisor or virtualization layer 1150, which maysometimes be referred to as a virtual machine monitor (VMM).Virtualization layer 1150 may present a virtual operating platform thatappears like networking hardware to virtual machine 1140.

As shown in FIG. 11, hardware 1130 may be a standalone network node withgeneric or specific components. Hardware 1130 may comprise antenna 11225and may implement some functions via virtualization. Alternatively,hardware 1130 may be part of a larger cluster of hardware (e.g. such asin a data center or customer premise equipment (CPE)) where manyhardware nodes work together and are managed via management andorchestration (MANO) 11100, which, among others, oversees lifecyclemanagement of applications 1120.

Virtualization of the hardware is in some contexts referred to asnetwork function virtualization (NFV). NFV may be used to consolidatemany network equipment types onto industry standard high volume serverhardware, physical switches, and physical storage, which can be locatedin data centers, and customer premise equipment.

In the context of NFV, virtual machine 1140 may be a softwareimplementation of a physical machine that runs programs as if they wereexecuting on a physical, non-virtualized machine. Each of virtualmachines 1140, and that part of hardware 1130 that executes that virtualmachine, be it hardware dedicated to that virtual machine and/orhardware shared by that virtual machine with others of the virtualmachines 1140, forms a separate virtual network elements (VNE).

Still in the context of NFV, Virtual Network Function (VNF) isresponsible for handling specific network functions that run in one ormore virtual machines 1140 on top of hardware networking infrastructure1130 and corresponds to application 1120 in FIG. 11.

In some embodiments, one or more radio units 11200 that each include oneor more transmitters 11220 and one or more receivers 11210 may becoupled to one or more antennas 11225. Radio units 11200 may communicatedirectly with hardware nodes 1130 via one or more appropriate networkinterfaces and may be used in combination with the virtual components toprovide a virtual node with radio capabilities, such as a radio accessnode or a base station.

In some embodiments, some signalling can be effected with the use ofcontrol system 11230 which may alternatively be used for communicationbetween the hardware nodes 1130 and radio units 11200.

FIG. 12 illustrates an example telecommunication network connected viaan intermediate network to a host computer in accordance with certainembodiments. With reference to FIG. 12, in accordance with anembodiment, a communication system includes telecommunication network1210, such as a 3GPP-type cellular network, which comprises accessnetwork 1211, such as a radio access network, and core network 1214.Access network 1211 comprises a plurality of base stations 1212 a, 1212b, 1212 c, such as NBs, eNBs, gNBs or other types of wireless accesspoints, each defining a corresponding coverage area 1213 a, 1213 b, 1213c. Each base station 1212 a, 1212 b, 1212 c is connectable to corenetwork 1214 over a wired or wireless connection 1215. A first UE 1291located in coverage area 1213 c is configured to wirelessly connect to,or be paged by, the corresponding base station 1212 c. A second UE 1292in coverage area 1213 a is wirelessly connectable to the correspondingbase station 1212 a While a plurality of UEs 1291, 1292 are illustratedin this example, the disclosed embodiments are equally applicable to asituation where a sole UE is in the coverage area or where a sole UE isconnecting to the corresponding base station 1212.

Telecommunication network 1210 is itself connected to host computer1230, which may be embodied in the hardware and/or software of astandalone server, a cloud-implemented server, a distributed server oras processing resources in a server farm. Host computer 1230 may beunder the ownership or control of a service provider, or may be operatedby the service provider or on behalf of the service provider.Connections 1221 and 1222 between telecommunication network 1210 andhost computer 1230 may extend directly from core network 1214 to hostcomputer 1230 or may go via an optional intermediate network 1220.Intermediate network 1220 may be one of, or a combination of more thanone of, a public, private or hosted network; intermediate network 1220,if any, may be a backbone network or the Internet; in particular,intermediate network 1220 may comprise two or more sub-networks (notshown).

The communication system of FIG. 12 as a whole enables connectivitybetween the connected UEs 1291, 1292 and host computer 1230. Theconnectivity may be described as an over-the-top (OTT) connection 1250.Host computer 1230 and the connected UEs 1291, 1292 are configured tocommunicate data and/or signaling via OTT connection 1250, using accessnetwork 1211, core network 1214, any intermediate network 1220 andpossible further infrastructure (not shown) as intermediaries. OTTconnection 1250 may be transparent in the sense that the participatingcommunication devices through which OTT connection 1250 passes areunaware of routing of uplink and downlink communications. For example,base station 1212 may not or need not be informed about the past routingof an incoming downlink communication with data originating from hostcomputer 1230 to be forwarded (e.g., handed over) to a connected UE1291. Similarly, base station 1212 need not be aware of the futurerouting of an outgoing uplink communication originating from the UE 1291towards the host computer 1230.

FIG. 13 illustrates an example host computer communicating via a basestation with a user equipment over a partially wireless connection, inaccordance with certain embodiment

Example implementations, in accordance with an embodiment, of the UE,base station and host computer discussed in the preceding paragraphswill now be described with reference to FIG. 13. In communication system1300, host computer 1310 comprises hardware 1315 including communicationinterface 1316 configured to set up and maintain a wired or wirelessconnection with an interface of a different communication device ofcommunication system 1300. Host computer 1310 further comprisesprocessing circuitry 1318, which may have storage and/or processingcapabilities. In particular, processing circuitry 1318 may comprise oneor more programmable processors, application-specific integratedcircuits, field programmable gate arrays or combinations of these (notshown) adapted to execute instructions. Host computer 1310 furthercomprises software 1311, which is stored in or accessible by hostcomputer 1310 and executable by processing circuitry 1318. Software 1311includes host application 1312. Host application 1312 may be operable toprovide a service to a remote user, such as UE 1330 connecting via OTTconnection 1350 terminating at UE 1330 and host computer 1310. Inproviding the service to the remote user, host application 1312 mayprovide user data which is transmitted using OTT connection 1350.

Communication system 1300 further includes base station 1320 provided ina telecommunication system and comprising hardware 1325 enabling it tocommunicate with host computer 1310 and with UE 1330. Hardware 1325 mayinclude communication interface 1326 for setting up and maintaining awired or wireless connection with an interface of a differentcommunication device of communication system 1300, as well as radiointerface 1327 for setting up and maintaining at least wirelessconnection 1370 with UE 1330 located in a coverage area (not shown inFIG. 13) served by base station 1320. Communication interface 1326 maybe configured to facilitate connection 1360 to host computer 1310.Connection 1360 may be direct or it may pass through a core network (notshown in FIG. 13) of the telecommunication system and/or through one ormore intermediate networks outside the telecommunication system. In theembodiment shown, hardware 1325 of base station 1320 further includesprocessing circuitry 1328, which may comprise one or more programmableprocessors, application-specific integrated circuits, field programmablegate arrays or combinations of these (not shown) adapted to executeinstructions. Base station 1320 further has software 1321 storedinternally or accessible via an external connection.

Communication system 1300 further includes UE 1330 already referred to.Its hardware 1335 may include radio interface 1337 configured to set upand maintain wireless connection 1370 with a base station serving acoverage area in which UE 1330 is currently located. Hardware 1335 of UE1330 further includes processing circuitry 1338, which may comprise oneor more programmable processors, application-specific integratedcircuits, field programmable gate arrays or combinations of these (notshown) adapted to execute instructions. UE 1330 further comprisessoftware 1331, which is stored in or accessible by UE 1330 andexecutable by processing circuitry 1338. Software 1331 includes clientapplication 1332. Client application 1332 may be operable to provide aservice to a human or non-human user via UE 1330, with the support ofhost computer 1310. In host computer 1310, an executing host application1312 may communicate with the executing client application 1332 via OTTconnection 1350 terminating at UE 1330 and host computer 1310. Inproviding the service to the user, client application 1332 may receiverequest data from host application 1312 and provide user data inresponse to the request data. OTT connection 1350 may transfer both therequest data and the user data. Client application 1332 may interactwith the user to generate the user data that it provides.

It is noted that host computer 1310, base station 1320 and UE 1330illustrated in FIG. 13 may be similar or identical to host computer1230, one of base stations 1212 a, 1212 b, 1212 c and one of UEs 1291,1292 of FIG. 12, respectively. This is to say, the inner workings ofthese entities may be as shown in FIG. 13 and independently, thesurrounding network topology may be that of FIG. 12.

In FIG. 13, OTT connection 1350 has been drawn abstractly to illustratethe communication between host computer 1310 and UE 1330 via basestation 1320, without explicit reference to any intermediary devices andthe precise routing of messages via these devices. Networkinfrastructure may determine the routing, which it may be configured tohide from UE 1330 or from the service provider operating host computer1310, or both. While OTT connection 1350 is active, the networkinfrastructure may further take decisions by which it dynamicallychanges the routing (e.g., on the basis of load balancing considerationor reconfiguration of the network).

Wireless connection 1370 between UE 1330 and base station 1320 is inaccordance with the teachings of the embodiments described throughoutthis disclosure. One or more of the various embodiments improve theperformance of OTT services provided to UE 1330 using OTT connection1350, in which wireless connection 1370 forms the last segment. Moreprecisely, the teachings of these embodiments may improve the signalingoverhead.

A measurement procedure may be provided for the purpose of monitoringdata rate, latency and other factors on which the one or moreembodiments improve. There may further be an optional networkfunctionality for reconfiguring OTT connection 1350 between hostcomputer 1310 and UE 1330, in response to variations in the measurementresults. The measurement procedure and/or the network functionality forreconfiguring OTT connection 1350 may be implemented in software 1311and hardware 1315 of host computer 1310 or in software 1331 and hardware1335 of UE 1330, or both. In embodiments, sensors (not shown) may bedeployed in or in association with communication devices through whichOTT connection 1350 passes; the sensors may participate in themeasurement procedure by supplying values of the monitored quantitiesexemplified above, or supplying values of other physical quantities fromwhich software 1311, 1331 may compute or estimate the monitoredquantities. The reconfiguring of OTT connection 1350 may include messageformat, retransmission settings, preferred routing etc.; thereconfiguring need not affect base station 1320, and it may be unknownor imperceptible to base station 1320. Such procedures andfunctionalities may be known and practiced in the art. In certainembodiments, measurements may involve proprietary UE signalingfacilitating host computer 1310's measurements of throughput,propagation times, latency and the like. The measurements may beimplemented in that software 1311 and 1331 causes messages to betransmitted, in particular empty or ‘dummy’ messages, using OTTconnection 1350 while it monitors propagation times, errors etc.

FIG. 14 is a flowchart illustrating an example method implemented in acommunication system, in accordance certain embodiments. Moreparticularly, FIG. 14 illustrates an example method implemented in acommunication system including a host computer, a base station and auser equipment. The communication system includes a host computer, abase station and a UE which may be those described with reference toFIGS. 12 and 13. For simplicity of the present disclosure, only drawingreferences to FIG. 14 will be included in this section. In step 1410,the host computer provides user data. In substep 1411 (which may beoptional) of step 1410, the host computer provides the user data byexecuting a host application. In step 1420, the host computer initiatesa transmission carrying the user data to the UE. In step 1430 (which maybe optional), the base station transmits to the UE the user data whichwas carried in the transmission that the host computer initiated, inaccordance with the teachings of the embodiments described throughoutthis disclosure. In step 1440 (which may also be optional), the UEexecutes a client application associated with the host applicationexecuted by the host computer.

FIG. 15 is a flowchart illustrating a second example method implementedin a communication system, in accordance with certain embodiments. Moreparticularly, FIG. 15 illustrates an example method implemented in acommunication system including a host computer, a base station and auser equipment. The communication system includes a host computer, abase station and a UE which may be those described with reference toFIGS. 12 and 13. For simplicity of the present disclosure, only drawingreferences to FIG. 15 will be included in this section. In step 1510 ofthe method, the host computer provides user data. In an optional substep(not shown) the host computer provides the user data by executing a hostapplication. In step 1520, the host computer initiates a transmissioncarrying the user data to the UE. The transmission may pass via the basestation, in accordance with the teachings of the embodiments describedthroughout this disclosure. In step 1530 (which may be optional), the UEreceives the user data carried in the transmission.

FIG. 16 is a flowchart illustrating a third method implemented in acommunication system, in accordance with certain embodiments. Moreparticularly, FIG. 16 illustrates an example method implemented in acommunication system including a host computer, a base station and auser equipment. The communication system includes a host computer, abase station and a UE which may be those described with reference toFIGS. 12 and 13. For simplicity of the present disclosure, only drawingreferences to FIG. 16 will be included in this section. In step 1610(which may be optional), the UE receives input data provided by the hostcomputer. Additionally or alternatively, in step 1620, the UE providesuser data. In substep 1621 (which may be optional) of step 1620, the UEprovides the user data by executing a client application. In substep1611 (which may be optional) of step 1610, the UE executes a clientapplication which provides the user data in reaction to the receivedinput data provided by the host computer. In providing the user data,the executed client application may further consider user input receivedfrom the user. Regardless of the specific manner in which the user datawas provided, the UE initiates, in substep 1630 (which may be optional),transmission of the user data to the host computer. In step 1640 of themethod, the host computer receives the user data transmitted from theUE, in accordance with the teachings of the embodiments describedthroughout this disclosure.

FIG. 17 is a flowchart illustrating a fourth method implemented in acommunication system, in accordance with certain embodiments. Moreparticularly, FIG. 17 illustrates an example method implemented in acommunication system including a host computer, a base station and auser equipment. The communication system includes a host computer, abase station and a UE which may be those described with reference toFIGS. 12 and 13. For simplicity of the present disclosure, only drawingreferences to FIG. 17 will be included in this section. In step 1710(which may be optional), in accordance with the teachings of theembodiments described throughout this disclosure, the base stationreceives user data from the UE. In step 1720 (which may be optional),the base station initiates transmission of the received user data to thehost computer. In step 1730 (which may be optional), the host computerreceives the user data carried in the transmission initiated by the basestation.

Certain example embodiments contemplated by the present disclosure aredescribed below. Note that the enumerated embodiments below are forpurposes of example only, and the present disclosure is not limited tothe example embodiments enumerated below.

Group A Embodiments

1. A method performed by a wireless device for transmitting a channelstate information (CSI) report indicating a plurality of precodervectors, wherein each precoder vector corresponds to a frequencysub-band and comprises linear combinations of spatial-domain componentsand frequency-domain components, and wherein the plurality of precodervectors is indicated by a set of coefficients of the linear combinationsand the frequency-domain components, the method comprising:

-   -   estimating a channel, and based on the estimated channel:        -   i. obtaining a first set of candidate frequency-domain            components,        -   ii. determining a set of spatial-domain components;        -   iii. determining a second set of candidate frequency-domain            components as a subset of the first set of candidate            frequency-domain components;        -   iv. determining, for each spatial-domain component of the            set, a spatial-domain component-specific subset of            frequency-domain components from the second set of candidate            frequency-domain components, wherein each component in the            spatial-domain component-specific subset of frequency-domain            components is associated with one or more linear combining            coefficients; and        -   v. transmitting, to a network node, a CSI report comprising            an indication of the determined second set of candidate            frequency-domain components and an indication of the            determined spatial-domain component-specific subsets of            frequency-domain components.            2. The method of embodiment 1, wherein the CSI report            further comprises the set of coefficients of the linear            combinations.            3. The method of any of embodiments 1-2, wherein the CSI            report further comprises one or more second sets of linear            combining coefficients, each second set of one or more            linear combining coefficients associated with a            spatial-domain component.            4. The method of any of embodiments 1-3, wherein determining            the second set of candidate frequency-domain components as a            subset of the first set of candidate frequency-domain            components comprises:    -   analyzing the estimated channel to determine one or more        properties of the channel; and    -   selecting the second set of candidate frequency-domain        components based on the determined one or more properties of the        channel.        5. The method of any of embodiments 1-4, wherein the candidate        frequency-components are orthogonal basis vectors.        6. The method of embodiment 5, wherein the orthogonal basis        vectors are discrete Fourier transform vectors.        7. The method of any of embodiments 1-6, wherein a size of the        frequency sub-band is one physical resource block (PRB).        8. The method of any of embodiments 1-6, wherein a size of the        frequency sub-band is an integer number of physical resource        blocks (PRBs).        9. The method of any of embodiments 1-8, wherein determining a        spatial-domain component-specific subset of frequency-domain        components comprises determining if the associated one or more        linear combining coefficients are non-zero.        10. The method of embodiment 9, wherein transmitting an        indication of the determined spatial-domain component-specific        subsets of frequency-domain components comprises transmitting an        indication of non-zero linear combining coefficients.        11. The method of any of embodiments 1-10, wherein obtaining the        first set of candidate frequency-domain components comprises        defining a first basis constituting a number of basis vectors.        12. The method of any of embodiments 1-11, wherein obtaining the        first set of candidate frequency-domain components comprises one        of.    -   accessing a predefined table;    -   obtaining the first set of candidate frequency-domain components        via higher layer signaling, and    -   determining the first set of candidate frequency-domain        components.        13. The method of any of embodiments 1-12, wherein the first set        of candidate frequency-domain components corresponds to an        oversampled discrete Fourier transform basis.        14. The method of any of embodiments 1-12, wherein the first set        of candidate frequency-domain components corresponds to an        orthogonal discrete Fourier transform basis.        15. The method of any of embodiments 1-14, wherein determining        the second set of candidate frequency-domain components as a        subset of the first set of candidate frequency-domain components        comprises:    -   selecting a subset of the first set of candidate        frequency-domain components to form a second set of candidate        frequency components.        16. The method of any of embodiments 1-14, wherein determining        the second set of candidate frequency-domain components as a        subset of the first set of candidate frequency-domain components        comprises:    -   creating a common basis for all spatial-domain components.        17. The method of embodiment 16, wherein the first set of        candidate frequency-domain components is a first basis matrix B        comprising K basis vectors.        18. The method of embodiment 17, further comprising:    -   selecting K_(c)<K columns of the first basis matrix B.        19. The method of embodiment 17, further comprising:    -   concatenating the selected columns K_(c) to form a common basis        matrix B_(c).        20. The method of embodiment 19, wherein the common basis matrix        B_(c) represents a channel and is used for both polarizations        and all layers in the precoder.        21. The method of embodiment 19, wherein the common basis matrix        B_(c) is chosen per one or more of polarization and layer.        22. The method of any of embodiments 1-21, comprising selecting        a spatial-domain component-specific basis from the second set of        candidate frequency-domain components.        23. The method of embodiment 22, wherein selecting a        spatial-domain component-specific basis from the second set of        candidate frequency-domain components comprises:    -   selecting a selection of columns from a common basis B_(c).        24. The method of any of the previous embodiments, further        comprising:    -   providing user data; and    -   forwarding the user data to a host computer via the transmission        to the base station.

Group B Embodiments

25. A method performed by a network node for receiving a channel stateinformation (CSI) report indicating a plurality of precoder vectors,wherein each precoder vector corresponds to a frequency sub-band andcomprises linear combinations of spatial-domain components andfrequency-domain components, and wherein the plurality of precodervectors is indicated by a set of coefficients of the linear combinationsand the frequency-domain components, the method comprising

-   -   receiving, from a wireless device, a channel state information        (CSI) report comprising an indication of a determined second set        of candidate-frequency domain components and an indication of        one or more determined spatial-domain component-specific subsets        of frequency-domain components; and    -   determining one or more precoder vectors based upon the received        indication of the determined second set of candidate-frequency        domain components and the indication of one or more determined        spatial-domain component-specific subsets of frequency-domain        components.        26. The method of embodiment 25, further comprising:    -   using one of the determined one or more precoder vectors to        perform a transmission to the wireless device.        27. The method of embodiment 25, further comprising:    -   using a different precoder vector from the one or more        determined precoder vectors to perform a transmission to the        wireless device.        28. The method of any of embodiments 25-27, wherein determining        one or more precoder vectors based upon the received indication        of the determined second set of candidate-frequency domain        components and the indication of one or more determined        spatial-domain component-specific subsets of frequency-domain        components comprises:    -   determining, from the spatial-domain component-specific subset        of frequency-domain components, one or more spatial-domain        components, wherein each component in the spatial-domain        component-specific subset of frequency-domain components is        associated with one or more linear combining coefficients;    -   determining a first set of candidate frequency-domain        components, the first set of candidate frequency-domain        components comprising the second set of candidate        frequency-domain components; and    -   determining a set of spatial-domain components.        29. The method of any of embodiments 25-28, wherein the        candidate frequency-components are orthogonal basis vectors.        30. The method of embodiment 29, wherein the orthogonal basis        vectors are discrete Fourier transform vectors;        31. The method of any of embodiments 25-30, wherein a size of        the frequency sub-band is one physical resource block (PRB).        32. The method of any of embodiments 25-30, wherein a size of        the frequency sub-band is an integer number of physical resource        blocks (PRBs).        33. The method of any of the previous embodiments, further        comprising.    -   obtaining user data; and    -   forwarding the user data to a host computer or a wireless        device.

Group C Embodiments

34. A wireless device, the wireless device comprising:

-   -   processing circuitry configured to perform any of the steps of        any of the Group A embodiments, and    -   power supply circuitry configured to supply power to the        wireless device.        35. A network node, the network node comprising:    -   processing circuitry configured to perform any of the steps of        any of the Group B embodiments;    -   power supply circuitry configured to supply power to the network        node.        36. A user equipment (UE), the UE comprising:    -   an antenna configured to send and receive wireless signals;    -   radio front-end circuitry connected to the antenna and to        processing circuitry, and configured to condition signals        communicated between the antenna and the processing circuitry;    -   the processing circuitry being configured to perform any of the        steps of any of the Group A embodiments;    -   an input interface connected to the processing circuitry and        configured to allow input of information into the UE to be        processed by the processing circuitry;    -   an output interface connected to the processing circuitry and        configured to output information from the UE that has been        processed by the processing circuitry; and    -   a battery connected to the processing circuitry and configured        to supply power to the UE.        37. A computer program, the computer program comprising        instructions which when executed on a computer perform any of        the steps of any of the Group A embodiments.        38. A computer program product comprising a computer program,        the computer program comprising instructions which when executed        on a computer perform any of the steps of any of the Group A        embodiments.        39. A non-transitory computer-readable storage medium or carrier        comprising a computer program, the computer program comprising        instructions which when executed on a computer perform any of        the steps of any of the Group A embodiments.        40. A computer program, the computer program comprising        instructions which when executed on a computer perform any of        the steps of any of the Group B embodiments.        41. A computer program product comprising a computer program,        the computer program comprising instructions which when executed        on a computer perform any of the steps of any of the Group B        embodiments.        42. A non-transitory computer-readable storage medium or carrier        comprising a computer program, the computer program comprising        instructions which when executed on a computer perform any of        the steps of any of the Group B embodiments.        43. A communication system including a host computer comprising:    -   processing circuitry configured to provide user data; and    -   a communication interface configured to forward the user data to        a cellular network for transmission to a user equipment (UE),    -   wherein the cellular network comprises a network node having a        radio interface and processing circuitry, the network node's        processing circuitry configured to perform any of the steps of        any of the Group B embodiments.        44. The communication system of the pervious embodiment further        including the network node.        45. The communication system of the previous 2 embodiments,        further including the UE, wherein the UE is configured to        communicate with the network node.        46. The communication system of the previous 3 embodiments,        wherein    -   the processing circuitry of the host computer is configured to        execute a host application, thereby providing the user data; and    -   the UE comprises processing circuitry configured to execute a        client application associated with the host application.        47. A method implemented in a communication system including a        host computer, a network node and a user equipment (UE), the        method comprising:    -   at the host computer, providing user data; and    -   at the host computer, initiating a transmission carrying the        user data to the UE via a cellular network comprising the        network node, wherein the network node performs any of the steps        of any of the Group B embodiments.        48. The method of the previous embodiment, further comprising,        at the network node, transmitting the user data.        49. The method of the previous 2 embodiments, wherein the user        data is provided at the host computer by executing a host        application, the method further comprising, at the LE, executing        a client application associated with the host application.        50. A user equipment (UE) configured to communicate with a        network node, the UE comprising a radio interface and processing        circuitry configured to performs the of the previous 3        embodiments.        51. A communication system including a host computer comprising:    -   processing circuitry configured to provide user data; and    -   a communication interface configured to forward user data to a        cellular network for transmission to a user equipment (UE),    -   wherein the UE comprises a radio interface and processing        circuitry, the UE's components configured to perform any of the        steps of any of the Group A embodiments.        52. The communication system of the previous embodiment, wherein        the cellular network further includes a network node configured        to communicate with the UE.        53. The communication system of the previous 2 embodiments,        wherein:    -   the processing circuitry of the host computer is configured to        execute a host application, thereby providing the user data; and    -   the UE's processing circuitry is configured to execute a client        application associated with the host application.        54. A method implemented in a communication system including a        host computer, a network node and a user equipment (UE), the        method comprising:    -   at the host computer, providing user data; and    -   at the host computer, initiating a transmission carrying the        user data to the UE via a cellular network comprising the        network node, wherein the UE performs any of the steps of any of        the Group A embodiments.        55. The method of the previous embodiment, further comprising at        the UE, receiving the user data from the network node.        56. A communication system including a host computer comprising:    -   communication interface configured to receive user data        originating from a transmission from a user equipment (UE) to a        network node,    -   wherein the UE comprises a radio interface and processing        circuitry, the UE's processing circuitry configured to perform        any of the steps of any of the Group A embodiments.        57. The communication system of the previous embodiment, further        including the UE.        58. The communication system of the previous 2 embodiments,        further including the network node, wherein the network node        comprises a radio interface configured to communicate with the        UE and a communication interface configured to forward to the        host computer the user data carried by a transmission from the        UE to the network node.        59. The communication system of the previous 3 embodiments,        wherein:    -   the processing circuitry of the host computer is configured to        execute a host application; and    -   the UE's processing circuitry is configured to execute a client        application associated with the host application, thereby        providing the user data.        60. The communication system of the previous 4 embodiments,        wherein:    -   the processing circuitry of the host computer is configured to        execute a host application, thereby providing request data; and    -   the UE's processing circuitry is configured to execute a client        application associated with the host application, thereby        providing the user data in response to the request data.        61. A method implemented in a communication system including a        host computer, a network node and a user equipment (UE), the        method comprising:    -   at the host computer, receiving user data transmitted to the        network node from the UE, wherein the UE performs any of the        steps of any of the Group A embodiments.        62. The method of the previous embodiment, further comprising,        at the UE, providing the user data to the network node.        63. The method of the previous 2 embodiments, further        comprising:    -   at the UE, executing a client application, thereby providing the        user data to be transmitted; and    -   at the host computer, executing a host application associated        with the client application.        64. The method of the previous 3 embodiments, further        comprising:    -   at the UE, executing a client application; and    -   at the UE, receiving input data to the client application, the        input data being provided at the host computer by executing a        host application associated with the client application,    -   wherein the user data to be transmitted is provided by the        client application in response to the input data.        65. A communication system including a host computer comprising        a communication interface configured to receive user data        originating from a transmission from a user equipment (UE) to a        network node, wherein the network node comprises a radio        interface and processing circuitry, the network node's        processing circuitry configured to perform any of the steps of        any of the Group B embodiments.        66. The communication system of the previous embodiment further        including the network node.        67. The communication system of the previous 2 embodiments,        further including the UE, wherein the UE is configured to        communicate with the network node.        68. The communication system of the previous 3 embodiments,        wherein:    -   the processing circuitry of the host computer is configured to        execute a host application;    -   the UE is configured to execute a client application associated        with the host application, thereby providing the user data to be        received by the host computer.        69. A method implemented in a communication system including a        host computer, a network node and a user equipment (UE), the        method comprising:    -   at the host computer, receiving, from the network node, user        data originating from a transmission which the network node has        received from the UE, wherein the UE performs any of the steps        of any of the Group A embodiments.        70. The method of the previous embodiment, further comprising at        the network node, receiving the user data from the UE.        71 The method of the previous 2 embodiments, further comprising        at the network node, initiating a transmission of the received        user data to the host computer.

Modifications, additions, or omissions may be made to the systems andapparatuses described herein without departing from the scope of thedisclosure. The components of the systems and apparatuses may beintegrated or separated. Moreover, the operations of the systems andapparatuses may be performed by more, fewer, or other components.Additionally, operations of the systems and apparatuses may be performedusing any suitable logic comprising software, hardware, and/or otherlogic. As used in this document, “each” refers to each member of a setor each member of a subset of a set.

Modifications, additions, or omissions may be made to the methodsdescribed herein without departing from the scope of the disclosure. Themethods may include more, fewer, or other steps. Additionally, steps maybe performed in any suitable order.

Although this disclosure has been described in terms of certainembodiments, alterations and permutations of the embodiments will beapparent to those skilled in the art. Accordingly, the above descriptionof the embodiments does not constrain this disclosure. Other changes,substitutions, and alterations are possible without departing from thespirit and scope of this disclosure, as defined by the following claims.

At least some of the following abbreviations may be used in thisdisclosure. If there is an inconsistency between abbreviations,preference should be given to how it is used above. If listed multipletimes below, the first listing should be preferred over any subsequentlisting(s).

-   1×RTT CDMA2000 1× Radio Transmission Technology-   3GPP 3rd Generation Partnership Project-   5G 5th Generation-   ABS Almost Blank Subframe-   ARQ Automatic Repeat Request-   AWGN Additive White Gaussian Noise-   BCCH Broadcast Control Channel-   BCH Broadcast Channel-   BWP Bandwidth Part-   CA Carrier Aggregation-   CC Carrier Component-   CCCH SDU Common Control Channel SDU-   CDMA Code Division Multiplexing Access-   CGI Cell Global Identifier-   CIR Channel Impulse Response-   CP Cyclic Prefix-   CPICH Common Pilot Channel-   CPICH Ec/No CPICH Received energy per chip divided by the power    density in the band-   CQI Channel Quality information-   CQIs Channel Quality Indicators-   C-RNTI Cell RNTI-   CRI CSI-RS Resource Indicator-   CSI Channel State Information-   CSI-RS Channel State Information Reference Signal-   DCCH Dedicated Control Channel-   DFT Discrete Fourier Transform-   DL Downlink-   DM Demodulation-   DMRS Demodulation Reference Signal-   DRX Discontinuous Reception-   DTX Discontinuous Transmission-   DTCH Dedicated Traffic Channel-   DUT Device Under Test-   E-CID Enhanced Cell-ID (positioning method)-   E-SMLC Evolved-Serving Mobile Location Centre-   ECGI Evolved CGI-   eNB E-UTRAN NodeB-   ePDCCH enhanced Physical Downlink Control Channel-   E-SMLC evolved Serving Mobile Location Center-   E-UTRA Evolved UTRA-   E-UTRAN Evolved UTRAN-   FDD Frequency Division Duplex-   FFS For Further Study-   GERAN GSM EDGE Radio Access Network-   gNB Base station in NR-   GNSS Global Navigation Satellite System-   GSM Global System for Mobile communication-   HARQ Hybrid Automatic Repeat Request-   HO Handover-   HSPA High Speed Packet Access-   HRPD High Rate Packet Data-   IMR Interference Measurement Resource-   LOS Line of Sight-   LPP LTE Positioning Protocol-   LTE Long-Term Evolution-   MAC Medium Access Control-   MBMS Multimedia Broadcast Multicast Services-   MBSFN Multimedia Broadcast multicast service Single Frequency    Network-   MBSFN ABS MBSFN Almost Blank Subframe-   MCS Modulation and Coding Scheme-   MDT Minimization of Drive Tests-   MIB Master Information Block-   MIMO Multiple-Input Multiple Output-   MME Mobility Management Entity-   MSC Mobile Switching Center-   MU-MIMO Multi-User MIMO-   NPDCCH Narrowband Physical Downlink Control Channel-   NR New Radio-   NZP Non-Zero Power-   OCNG OFDMA Channel Noise Generator-   OFDM Orthogonal Frequency Division Multiplexing-   OFDMA Orthogonal Frequency Division Multiple Access-   OSS Operations Support System-   OTDOA Observed Time Difference of Arrival-   O&M Operation and Maintenance-   PBCH Physical Broadcast Channel-   P-CCPCH Primary Common Control Physical Channel-   PCell Primary Cell-   PCFICH Physical Control Format Indicator Channel-   PDCCH Physical Downlink Control Channel-   PDP Profile Delay Profile-   PDSCH Physical Downlink Shared Channel-   PGW Packet Gateway-   PHICH Physical Hybrid-ARQ Indicator Channel-   PLMN Public Land Mobile Network-   PMI Precoder Matrix Indicator-   PRACH Physical Random Access Channel-   PRB Physical Resource Block-   PRS Positioning Reference Signal-   PSS Primary Synchronization Signal-   PUCCH Physical Uplink Control Channel-   PUSCH Physical Uplink Shared Channel-   RACH Random Access Channel-   QAM Quadrature Amplitude Modulation-   RAN Radio Access Network-   RAT Radio Access Technology-   RE Resource Element-   RI Rank Indicator-   RLM Radio Link Management-   RNC Radio Network Controller-   RNTI Radio Network Temporary Identifier-   RRC Radio Resource Control-   RRM Radio Resource Management-   RS Reference Signal-   RSCP Received Signal Code Power-   RSRP Reference Symbol Received Power OR-   Reference Signal Received Power-   RSRQ Reference Signal Received Quality OR-   Reference Symbol Received Quality-   RSSI Received Signal Strength Indicator-   RSTD Reference Signal Time Difference-   SCH Synchronization Channel-   SCell Secondary Cell-   SDU Service Data Unit-   SFN System Frame Number-   SGW Serving Gateway-   SI System Information-   SIB System Information Block-   SNR Signal to Noise Ratio-   SON Self Optimized Network-   SS Synchronization Signal-   SSS Secondary Synchronization Signal-   TDD Time Division Duplex-   TDOA Time Difference of Arrival-   TFRE Time Frequency Resource Element-   TOA Time of Arrival-   TSS Tertiary Synchronization Signal-   TTI Transmission Time Interval-   UE User Equipment-   UL Uplink-   ULA Uniform Linear Array-   UMTS Universal Mobile Telecommunication System-   UPA Uniform Planar Array-   USIM Universal Subscriber Identity Module-   UTDOA Uplink Time Difference of Arrival-   UTRA Universal Terrestrial Radio Access-   UTRAN Universal Terrestrial Radio Access Network-   WCDMA Wide CDMA-   WLAN Wide Local Area Network

The invention claimed is:
 1. A method performed by a wireless device fortransmitting a channel state information (CSI) report for a downlinkchannel, the CSI report indicating a plurality of precoder vectors,wherein each of the precoder vectors corresponds to a frequency sub-bandof the bandwidth of the downlink channel, a precoder vector beingexpressed as a linear combination of spatial-domain components andfrequency-domain components, and wherein indicating the plurality ofprecoder vectors comprises indicating the frequency-domain componentsand a set of linear combination coefficients, the method comprising:determining a set of spatial-domain components; determining a second setof candidate frequency-domain components as a subset of a first set ofcandidate frequency-domain components, wherein the second set ofcandidate frequency-domain components is smaller than the first set ofcandidate frequency-domain components; determining, for eachspatial-domain component of the set of spatial-domain components, aspatial-domain component-specific set of one or more frequency-domaincomponents by selecting a subset of the candidate frequency-domaincomponents from the second set of candidate frequency-domain componentsto be used for that spatial-domain component, wherein the subset of thecandidate frequency-domain components from the second set is smallerthan the second set and, wherein each frequency-domain component in thespatial-domain component-specific set of one or more frequency-domaincomponents is associated with a non-zero coefficient of the set oflinear combination coefficients; and transmitting, to a network node,the CSI report comprising an indication of: the determined second set ofcandidate frequency-domain components; the determined spatial-domaincomponent-specific sets of one or more frequency-domain components; andthe non-zero coefficients of the set of linear combination coefficients.2. The method of claim 1, wherein, for at least one spatial-domaincomponent, the spatial-domain component-specific set of one or morefrequency-domain components includes fewer frequency-domain componentsthan the second set of candidate frequency-domain components.
 3. Themethod of any claim 1, wherein the candidate frequency-domain componentsare orthogonal basis vectors.
 4. The method of claim 2, wherein theorthogonal basis vectors are discrete Fourier transform vectors.
 5. Themethod of claim 1, wherein a size of the frequency sub-band is aninteger number of physical resource blocks (PRBs).
 6. The method ofclaim 1, wherein determining the second set of candidatefrequency-domain components as the subset of the first set of candidatefrequency-domain components comprises: creating a common basis for allthe spatial-domain components.
 7. A method performed by a network nodefor receiving a channel state information (CSI) report for a downlinkchannel, the CSI report indicating a plurality of precoder vectors,wherein each of the precoder vectors corresponds to a frequency sub-bandof the bandwidth of the downlink channel, a precoder vector beingexpressed as a linear combination of spatial-domain components andfrequency-domain components, and wherein indicating the plurality ofprecoder vectors comprises indicating the frequency-domain componentsand a set of linear combination coefficients, the method comprising:receiving, from a wireless device, the channel state information (CSI)report comprising an indication of: a second set of candidatefrequency-domain components being a subset of a first set of candidatefrequency-domain components, wherein the second set of candidatefrequency-domain components is smaller than the first set of candidatefrequency-domain components; one or more spatial-domaincomponent-specific sets of one or more frequency-domain components whichare selected as one or more subsets of the second set of candidatefrequency-domain components, wherein at least one of the selected one ormore subsets of the second set is smaller than the second set eachfrequency-domain component in the one or more spatial-domaincomponent-specific sets of one or more frequency-domain components beingassociated with a non-zero coefficient of the set of linear combinationcoefficients; and the non-zero coefficients; and determining one or moreprecoder vectors based upon the indication received in the CSI report.8. The method of claim 7, wherein, for at least one spatial-domaincomponent, the spatial-domain component-specific set of one or morefrequency-domain components includes fewer frequency-domain componentsthan the second set of candidate frequency-domain components.
 9. Themethod of claim 7, further comprising: using one of the determined oneor more precoder vectors to perform a transmission to the wirelessdevice.
 10. The method of claim 7, wherein a size of the frequencysub-band is an integer number of physical resource blocks (PRBs).
 11. Awireless device configured to transmit a channel state information (CSI)report for a downlink channel, the CSI report indicating a plurality ofprecoder vectors, wherein each of the precoder vectors corresponds to afrequency sub-band of the bandwidth of the downlink channel, a precodervector being expressed as a linear combination of spatial-domaincomponents and frequency-domain components, and wherein indicating theplurality of precoder vectors comprises indicating the frequency-domaincomponents and a set of linear combination coefficients, the wirelessdevice comprising: a receiver; a transmitter; and processing circuitrycoupled to the receiver and the transmitter, the processing circuitryconfigured to: determine a set of spatial-domain components; determine asecond set of candidate frequency-domain components as a subset of afirst set of candidate frequency-domain components, wherein the secondset of candidate frequency-domain components is smaller than the firstset of candidate frequency-domain components; determine, for eachspatial-domain component of the set of spatial-domain components, aspatial-domain component-specific set of one or more frequency-domaincomponents by selecting a subset of the candidate frequency-domaincomponents from the second set of candidate frequency-domain componentsto be used for that spatial-domain component, wherein the subset ofcandidate frequency-domain components from the second set is smallerthan the second set, wherein each frequency-domain component in thespatial-domain component-specific set of one or more frequency-domaincomponents is associated with a non-zero coefficient of the set oflinear combination coefficients; and transmit, to a network node, theCSI report comprising an indication of: the determined second set ofcandidate frequency-domain components; the determined spatial-domaincomponent-specific sets of one or more frequency-domain components; andthe non-zero coefficients of the set of linear combination coefficients.12. The wireless device of claim 11, wherein, for at least onespatial-domain component, the spatial-domain component-specific set ofone or more frequency-domain components includes fewer frequency-domaincomponents than the second set of candidate frequency-domain components.13. The wireless device of claim 11, wherein the candidatefrequency-domain components are orthogonal basis vectors.
 14. Thewireless device of claim 13, wherein the orthogonal basis vectors arediscrete Fourier transform vectors.
 15. The wireless device of claim 11,wherein a size of the frequency sub-band is an integer number ofphysical resource blocks (PRBs).
 16. The wireless device of claim 11,wherein the processing circuitry configured to determine the second setof candidate frequency-domain components as the subset of the first setof candidate frequency-domain components is further configured to:create a common basis for all the spatial-domain components.
 17. Anetwork node configured to receive a channel state information (CSI)report for a downlink channel, the CSI report indicating a plurality ofprecoder vectors, wherein each of the precoder vectors corresponds to afrequency sub-band of the bandwidth of the downlink channel, a precodervector being expressed as a linear combination of spatial-domaincomponents and frequency-domain components, and wherein indicating theplurality of precoder vectors comprises indicating the frequency-domaincomponents and a set of linear combination coefficients, the networknode comprising: a receiver; a transmitter; and processing circuitrycoupled to the receiver and the transmitter, the processing circuitryconfigured to: receive, from a wireless device, the channel stateinformation (CSI) report comprising an indication of: a second set ofcandidate frequency-domain components being a subset of a first set ofcandidate frequency-domain components, wherein the second set ofcandidate frequency-domain components is smaller than the first set ofcandidate frequency-domain components; one or more spatial-domaincomponent-specific sets of one or more frequency-domain components whichare selected as a subset of the second set of candidate frequency-domaincomponents, wherein the subset of the second set is smaller than thesecond set, each frequency-domain component in the one or morespatial-domain component-specific sets of one or more frequency-domaincomponents being associated with a non-zero coefficient of the set oflinear combination coefficients; and the non-zero coefficients; anddetermine one or more precoder vectors based upon the indicationreceived in the CSI report.
 18. The network node of claim 17, wherein,for at least one spatial-domain component, the spatial-domaincomponent-specific set of one or more frequency-domain componentsincludes fewer frequency-domain components than the second set ofcandidate frequency-domain components.
 19. The network node of claim 17,wherein the processing circuitry is further configured to: use one ofthe determined one or more precoder vectors to perform a transmission tothe wireless device.
 20. The network node of claim 17, wherein a size ofthe frequency sub-band is an integer number of physical resource blocks(PRBs).